Across
A bird traversing lake, a noted flyer (6)
I haven't cracked this one yet — but Fifteensquared have:
An envelope (‘traversing’) of L (‘lake’) in ‘a’ plus COCK (‘bird’), for Captain Sir John William ALCOCK, the pioneer aviator.
Protective plate supports gemstone (8)
Observe learner keeping quiet — backward type interacting weakly (6)
I haven't cracked this one yet — but Fifteensquared have:
A reversal (‘backward’) of an envelope (‘keeping’) of P ( piano , ‘quiet’) in NOTE (‘observe’) plus L (‘learner’).
Friendly note within an urgent message? (8)
I haven't cracked this one yet — but Fifteensquared have:
An envelope (‘within’) of MI (‘note’ of the sol-fa) in A CABLE (‘an urgent message’).
Aids to those researching wicked Etonian squires (14)
A submarine captain, first person to attempt meteorological technique (10)
Yield from what's sown in garden, reportedly (4)
Spoil vote, as one looking for revolution? (4)
Extended treatise penned by professional wordsmith (10)
Absence of instruments to welcome in golden prizewinners (5,9)
I haven't cracked this one yet — but Fifteensquared have:
An envelope (‘to welcome in’) of AUREATE (‘golden’) in NO BELLS (‘absence of instruments’).
Brief about pee containing metallic element (8)
Problem with this Roman vessel (6)
It's marvellous to celebrate drinking squash (8)
Parlay has a king thus functioning (2,4)
Down
Bar left in sack (4)
Catch caught on river, suitable for catching (7)
I haven't cracked this one yet — but Fifteensquared have:
An envelope (‘for catching’) of APT (‘suitable’) in C (‘caught’) plus URE (‘river’).
Weapon to pass through the East End? (8)
Payer regarding Spooner's dividend (11)
Amateur seaman turned up for party (6)
I haven't cracked this one yet — but Fifteensquared have:
A reversal (‘turned up’ in a down light) of LAIC (‘amateur’) plus OS (ordinary ‘seaman’).
Tavern's purple fruit not popular (7)
What's said to be terrible root crop or plant (5-4)
You might notice it in one bar, I fancy (11)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (‘fancy’) of ‘it in one bar I’, with an extended definition.
Fossils — a couple of thousand on new site (9)
I haven't cracked this one yet — but Fifteensquared have:
A charade of ‘a’ plus MM (‘Roman numeral or numerals, ‘a couple of thousand’) plus ‘on’ plus ITES, an anagram (‘new’) of ‘site’.
Swimming race — a time to dive in (8)
I haven't cracked this one yet — but Fifteensquared have:
An envelope (‘to dive in’) of ‘a’ plus T (‘time’) in NATION (‘race’).
Difficulty leads to jazz singer making a complaint (7)
Hawkish type with various cruelties putting us off (7)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (‘various’) of ‘cr[u]eltie[s]’ minus US (‘putting us off’). A TIERCEL or tercel is a male falcon.
Pilgrim's bad experience somewhere near Windsor (6)
Doctor shower's output, not right (4)
Type letters or click words in the clue