Bird bone's bitten off at both ends (3)
I believe the answer is:
emu
'bird' is the definition.
(emu is a kind of bird)
'bone's bitten off at both ends' is the wordplay.
'bone' becomes 'femur' (femur is a kind of bone).
'bitten off at both ends' indicates the central letters (the two end letters are removed).
The central letters of 'femur' are 'EMU'.
(Other definitions for emu that I've seen before include "Flightless bird of Australia, like ostrich" , "Aussie bird" , "European project" , "Big bird" , "it can't get off the ground" .)