Bird initially occupying small quarry (6)
I believe the answer is:
osprey
'bird' is the definition.
(osprey is a kind of bird)
'initially occupying small quarry' is the wordplay.
'initially' indicates taking the first letters.
'quarry' becomes 'prey' ('prey' can be a synonym of 'quarry').
The initial letters of 'occupying small' is 'os'.
'os'+'prey'='OSPREY'
(Other definitions for osprey that I've seen before include "Large bird preying on fish in inland waters" , "A feather trimming (6)" , "One flying" , "Piscivorous creature" , "Flier" .)