Spell of unrestrained activity (5)
I believe the answer is:
spree
'spell of unrestrained activity' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for spree that I've seen before include "Wild shopping expedition" , "booze-up?" , "night on the razzle?" , "Spell of wild activity" , "Bout of self-indulgence" .)