He has a bit of fun with a bird (3)
I believe the answer is:
hen
'bird' is the definition.
(hen is a kind of bird)
'he has a bit of fun' is the wordplay.
'has' is a charade indicator (letters next to each other).
'a bit of fun' becomes 'n' (I can't justify this - if you can you should give a lot more credence to this answer).
'he'+'n'='HEN'
'with a' is the link.
Can you help me to learn more?
(Other definitions for hen that I've seen before include "Clucking female" , "Composed of women" , "Coop resident" , "Insufficient in amount" , "Female bird" .)