Prepare to shoot a bird (4)
I believe the answer is:
cock
This clue is a double definition.
'prepare to shoot' is the first definition.
(I've seen this before)
'a bird' is the second definition.
(cock is a kind of bird)
(Other definitions for cock that I've seen before include "bull to > raise for shooting" , "Hens partner" , "sunshine" , "small pile of hay" , "Set upright" .)