Sound cure for cant (4)
I believe the answer is:
heel
'cant' is the definition.
(thesaurus)
'sound cure' is the wordplay.
'sound' indicates a 'sounds like' (homophone) clue.
'cure' becomes 'heal' ('heal' can be a synonym of 'cure').
'heal' is a homophone of 'HEEL'.
'for' is the link.
(Other definitions for heel that I've seen before include "villain" , "secure ball" , "Spur" , "3's weak point" , "Rogue" .)