Loose, large bag containing money (5)
I believe the answer is:
slack
'loose' is the definition.
(slacking is a kind of loosing)
'large bag containing money' is the wordplay.
'large bag' becomes 'sack' (I've seen this before).
'containing' is an insertion indicator.
'money' becomes 'l' (L can mean 'pounds').
'sack' going around 'l' is 'SLACK'.
(Other definitions for slack that I've seen before include "Idle and disinclined to work" , "Loose" , "Lax" , "Limp - negligent" , "skive" .)