Across
Cultivates grass in manure initially? (6)
Headcase swaps sides – it's something of a cliché (8)
Work together on article depicting financial investor (5)
Suffer naval disruption getting stuck inside deluge (9)
I haven't cracked this one yet — but Fifteensquared have:
*(naval) [anag: disruption ] getting stuck inside ACHE ("suffer")
Culture has potential for growth here? (5,4)
King takes in poet (5)
Victor expelled from crumbling private school somewhere in Greece (3,9)
It lets you have a say on boards? (8,4)
Working double around island to find some food (5)
I haven't cracked this one yet — but Fifteensquared have:
ON + ON ("working", double ) around I (island)
Tory sabre rattling in upmarket diner (6,3)
Old cat is tough, having a large family (9)
Clothing that's trendy in Dubai on vacation (5)
I haven't cracked this one yet — but Fifteensquared have:
HOT ("trendy") in D (uba) I [ on vacation ]
Cleans up occasional leaks spreading around 'below' (8)
I haven't cracked this one yet — but Fifteensquared have:
[ occasional ] L (e) A (k) S spreading around UNDER ("below")
Trimmed beef for example, knowing it's too small (6)
Down
Terribly drab old PM who's had many rôles (4,4)
I haven't cracked this one yet — but Fifteensquared have:
*(drab) [anag: terribly ] + (William) PITT (presumable the Elder) ("old PM")
Advanced years, when Thatcher was in her prime? (8)
Leading doctors envisage large health investment for city (5)
No one has birth as complicated as he imagined! (5,8)
Fantastic medical support includes recreational space (9)
Almost make out with sailor that's so sweet (6)
Belief is part of those who traditionally oppose us (6)
Handsome pupil perhaps (1,3,2,1,6)
I haven't cracked this one yet — but Fifteensquared have:
The pupil is part of the eye, so A BIT OF A LOOKER (that which looks)
Being humble, turned up to return lost headgear (3,2,4)
One has trouble getting into them – they're difficult to read (3,5)
Eight fallen over – it takes forever to understand its meaning (8)
I haven't cracked this one yet — but Fifteensquared have:
The INFINITY sign looks like an 8 that's "fallen over" and INFINITY and ETERNITY are similar concepts.
Huge amount of slime on backed-up register (6)
Note position on university scene (6)
Provide objective Brussels promoted (5)
I haven't cracked this one yet — but Fifteensquared have:
END ("objective") + <=EU (European Union, so "Brussels", promoted, i.e. pushed up)
Type letters or click words in the clue