Big fling (5)
I believe the answer is:
spree
'big fling' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for spree that I've seen before include "Period of extravagance or excess" , "Spending bout" , "Session of over-indulgence" , "A lively extravagant outing" , "night on the razzle?" .)