Welsh for example turned up supporting Frenchman (6)
I believe the answer is:
renege
'welsh' is the definition.
(thesaurus)
'example turned up supporting frenchman' is the wordplay.
'example' becomes 'eg'.
'turned up' is a reversal indicator.
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'frenchman' becomes 'rene'.
'eg' in reverse letter order is 'ge'.
'ge' put after 'rene' is 'RENEGE'.
'for' acts as a link.
(Other definitions for renege that I've seen before include "In card games, revoke" , "Don't follow suit when you can" , "Change one's mind" , "South American cowboy" , "Fail to carry out a commitment" .)