Fan to breed bird (8)
I believe the answer is:
nuthatch
'bird' is the definition.
(nuthatch is a kind of bird)
'fan to breed' is the wordplay.
'fan' becomes 'nut' (both can mean an enthusiast).
'to breed' becomes 'hatch' (I've seen this before).
'nut'+'hatch'='NUTHATCH'
(Other definitions for nuthatch that I've seen before include "Small songbird that climbs up and down trees looking for food" , "[FEATHERED FRIEND]" , "Bird - hunt chat (anag)" , "Songbird named from its penchant for a kind of fruit" , "Small songbird often seen on tree trunks" .)