Put a lid on (3)
I believe the answer is:
cap
'put a lid on' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cap that I've seen before include "Headgear item" , "Set limit to price increase - of headgear?" , "contribution to hunt funds?" , "Flat brimless hat" , "Soft hat; lid" .)