Greene novel in Welsh (6)
I believe the answer is:
renege
'welsh' is the definition.
(thesaurus)
'greene novel' is the wordplay.
'novel' indicates an anagram.
'greene' anagrammed gives 'RENEGE'.
'in' is the link.
(Other definitions for renege that I've seen before include "Fail to follow suit or fulfil a promise" , "Change one's mind" , "Go back (on promise etc)" , "Fail to follow suit at cards" , "Withdraw" .)