Game bird or chicken might do this (5)
I believe the answer is:
quail
This clue is a triple definition!
'game' is the first definition.
(I've seen this before)
'bird' is the second definition.
(quail is a kind of bird)
'or' is a link.
'chicken might do this' is the third definition.
(a cowardly person might quail)
(Other definitions for quail that I've seen before include "See little bird" , "Shrink; a bird" , "Game bird - cower" , "Small bird of the partridge family" , "Cower before the game-bird?" .)