Perhaps cur upset old thief (8)
I believe the answer is:
cutpurse
'old thief' is the definition.
(old term for a thief)
'perhaps cur upset' is the wordplay.
'perhaps' indicates an anagram.
'cur'+'upset'='curupset'
'curupset' anagrammed gives 'CUTPURSE'.
(Other definitions for cutpurse that I've seen before include "Old pickpocket - true cups (anag)" , "Pickpocket of olden times" , "robber" , "thief (not me!)" , "Pickpocket -- set up cru (anag)" .)