Restriction gets Bruce no end upset! (4)
I believe the answer is:
curb
'restriction' is the definition.
(thesaurus)
'bruce no end upset' is the wordplay.
'no end' means to remove the last letter.
'upset' shows that the letters should be reversed in order.
'bruce' with its final letter removed is 'bruc'.
'bruc' back-to-front is 'CURB'.
'gets' acts as a link.
(Other definitions for curb that I've seen before include "Muzzle" , "Restrain, perhaps your enthusiasm" , "'Temper, hold in restraint (4)'" , "Strap used to restrain horse" , "Restrain, inhibit" .)