Guns turn out to be warm (4)
I believe the answer is:
snug
'warm' is the definition.
(thesaurus)
'guns turn out' is the wordplay.
'turn out' indicates anagramming the letters.
'guns' with letters rearranged gives 'SNUG'.
'to be' is the link.
(Other definitions for snug that I've seen before include "Bar parlour - comfortably placed" , "Comfortabel with guns" , "Close-fitting and cosy" , "He joined" , "Comfortable with guns" .)