Bag a cash prize! (5)
I believe the answer is:
purse
I believe this clue is a double definition.
'bag' is the first definition.
(synonyms)
'a cash prize' is the second definition.
(I've seen this before)
(Other definitions for purse that I've seen before include "Prize in sporting contest" , "Money - contract" , "Prize funds" , "Small pouch for carrying money, mostly by women" , "Knit" .)