Curse faulty wares (5)
I believe the answer is:
swear
'curse' is the definition.
(I know that curse can be written as swear)
'faulty wares' is the wordplay.
'faulty' indicates anagramming the letters.
'wares' is an anagram of 'SWEAR'.
(Other definitions for swear that I've seen before include "Utter obscenities or take an oath" , "Assert" , "Vow, attest" , "Vow; blaspheme" , "Emit oath or take vow" .)