Bird's poorly -- took food to stimulate (9)
I believe the answer is:
titillate
'stimulate' is the definition.
(titillating is a kind of stimulating)
'bird's poorly took food' is the wordplay.
'bird' becomes 'tit' (I've seen this before).
'poorly' becomes 'ill' ('ill' can be a synonym of 'poorly').
'took food' becomes 'ate' (I've seen this before).
'tit'+'ill'+'ate'='TITILLATE'
'to' is the link.
(Other definitions for titillate that I've seen before include "Excite erotically" , "Stimulate agreeably" , "Excite through suggestive means" , "Tease" , "provide excitement" .)