Welsh like interrupting Frenchman (6)
I believe the answer is:
renege
'welsh' is the definition.
(thesaurus)
'like interrupting frenchman' is the wordplay.
'like' becomes 'eg' (I've seen this in other clues).
'interrupting' is an insertion indicator.
'frenchman' becomes 'rene' (common French name).
'eg' inserted into 'rene' is 'RENEGE'.
(Other definitions for renege that I've seen before include "Change one's mind" , "Fail to follow suit at cards" , "Fail to keep promise, or revoke in cards" , "In card games, revoke" , "Fail to carry out a commitment" .)