Group extremely blithe? Very (4)
I believe the answer is:
bevy
'group extremely' is the definition.
'bevy' can be an answer for 'group' (I've seen this before). I'm not sure about the 'extremely' bit.
'blithe? very' is the wordplay.
I cannot really understand how this works, but
'very' could be 'v' (abbreviation) and 'v' is found in the answer.
The remaining letters 'bey' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
(Other definitions for bevy that I've seen before include "many girls" , "Flock of larks; group of beautiful women" , "Flock of birds, girls or other groups" , "Pack" , "A large group - of beauties?" .)