Curb champ from time to time (3)
I believe the answer is:
cap
'curb' is the definition.
(both can mean an upper limit on something)
'champ from time to time' is the wordplay.
'from time to time' means one should take alternating letters (letters removed on a regular basis).
The alternate letters of 'champ' are 'CAP'.
(Other definitions for cap that I've seen before include "Set limit to price increase - of headgear?" , "Soft hat; crown" , "Soft headgear" , "Soft hat; lid" , "'If the . . . fits, wear it' (3" .)