Across
£500 (double the amount in cash) (6)
I haven't cracked this one yet — but Fifteensquared have:
An envelope (‘in’) of K (‘double the amount’ – that is, £1000, perhaps more commonly rendered as G, rather than K) in MONEY (‘cash’).
Man is one (except according to Donne!) (6)
I haven't cracked this one yet — but Fifteensquared have:
A reference to the quote from John Donne “No man is an island”.
Mystical style of Gangnam artist? (7)
After work, a priest knocks off (7)
Island natives spooked Argonauts and, ultimately, Jason (5-5)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (‘spooked’) of ‘Argonauts’ plus N (‘ultimately, Jaso N ‘). Orangutans (with or without the hyphen) are now found in the islands of Borneo and Sumatra.
Employed setters and someone more senior (4)
German publican’s spirit (5)
I haven't cracked this one yet — but Fifteensquared have:
A charade of G (‘German’) plus HOST (‘publican’).
One suspends cuts, recounting encounter with leader of 9 (4,4)
Spooner’s ‘kick in the pants’ drink (4,4)
I haven't cracked this one yet — but Fifteensquared have:
A Spoonerism of BOOT REAR (‘kick in the pants’).
From the mouth, heard by the ear (5)
Rocks back, kisses me, gently content (4)
Might those they work with be stingy? (10)
Ernie and Ritchie meet Alec, perhaps (4,3)
Behaves badly – boorish tussling’s no good (7)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (‘boorish’) of ‘tusslin[g]’ minus the G (‘no good’).
Batman’s thus indicated cloak? (6)
Like 13as, having no right to short notice (6)
Down
One doesn’t like spending time away from man (5)
Negative letters from company? Impossible! (2,3,2)
I haven't cracked this one yet — but Fifteensquared have:
A charade of NO (‘negative’) plsu C AND O (CO, ‘letters from company’).
Body of letter describes quite questionable manners (9)
Heading for Sandwich in small craft (5)
Looking to the sky, weighs up a task – it’s taken on if really necessary (2,1,4)
Passes Morlocks’ prey, left for fuel (6,3)
I haven't cracked this one yet — but Fifteensquared have:
A charade of DIES (‘passes’) plus ELOI (‘Morlocks’ prey’ – eaten by Morlocks in H.G. Wells’ The Time Machine) plus L (‘left’).
Handy plants for sandy shade? (4,5)
I haven't cracked this one yet — but Fifteensquared have:
Punning definition, with PALM for ‘handy’, and the association of palms with Saharan oases
Ordered cigs, unopened beer, or household supplies (9)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (‘ordered’) of ‘cigs’ plus ‘[b]eer’ minus its first letter (‘unopened’) plus ‘or’.
Trump’s slogan boosted men struggling against legendary warrior (9)
Teaching paper will be in Spanish as part of the bigger picture (7)
Part exchange delivered: you are last to receive transport (7)
I haven't cracked this one yet — but Fifteensquared have:
A charade of RAPT, an anagram (‘exchange’) of ‘part’ plus UR, sounding like (‘delivered’) ‘you are’, plus E (‘last to receiv E ‘).
Wild country with river running through shrubby area (5)
I haven't cracked this one yet — but Fifteensquared have:
An envelope (‘with … running through’) of R (‘river’) in BUSH (‘wild country’). I think that is the better interpretation of the clue structure, rather than taking ‘wild country’ as the definition.
Scored and wore away missing veneer (5)
Type letters or click words in the clue