Search for a gun (5)
I believe the answer is:
rifle
I believe this clue is a double definition.
'search' is the first definition.
(I know that rifle is a type of search)
'a gun' is the second definition.
(I know that Rifle is a type of piece)
'for' is the link.
(Other definitions for rifle that I've seen before include "Search with intent to steal" , "Carbine" , "Long-barrelled weapon, normal army equipment" , "Search and rob - with long gun?" , "Search and rob for army weapon" .)