Fire in bag (4)
I believe the answer is:
sack
I believe this is a double definition.
'fire' is the first definition.
('sack' can be a synonym of 'fire')
'bag' is the second definition.
(sack is a kind of bag)
'in' is the link.
(Other definitions for sack that I've seen before include "Large canvas bag" , "Plunder; wine; bag" , "Large hessian bag" , "Devastate" , "Fire the old drink?" .)