Game bird gets right marksman (6)
I believe the answer is:
sniper
'marksman' is the definition.
(I know that marksman can be written as sniper)
'game bird gets right' is the wordplay.
'game bird' becomes 'snipe' (I've seen this before).
'gets' is a charade indicator (letters next to each other).
'right' becomes 'r' (common abbreviation).
'snipe'+'r'='SNIPER'
(Other definitions for sniper that I've seen before include "Concealed sharpshooter" , "One firing from cover" , "Concealed gunner" , "Hidden gunman" , "Rifleman firing from concealed location" .)