Gun for poor flier (5)
I believe the answer is:
rifle
'gun' is the definition.
(I know that rifle is a type of firearm)
'poor flier' is the wordplay.
'poor' indicates anagramming the letters.
'flier' is an anagram of 'RIFLE'.
'for' acts as a link.
(Other definitions for rifle that I've seen before include "Go through in search" , "Shoulder firearm" , "Search with intent to steal" , "Gun - ransack" , "Sack; firearm" .)