Weapon is free in shelter (7)
I believe the answer is:
trident
'weapon' is the definition.
(trident is a kind of weapon)
'free in shelter' is the wordplay.
'free' becomes 'rid' (to be free of something is to be rid of it).
'in' indicates putting letters inside.
'shelter' becomes 'tent' (canvas shelter).
'rid' put inside 'tent' is 'TRIDENT'.
'is' is the link.
(Other definitions for trident that I've seen before include "Red tint (anag.)" , "Neptune's weapon" , "Nuclear weapon" , "Spear with three prongs" , "Neptune's fork" .)