Relish novel cause (5)
I believe the answer is:
sauce
'relish' is the definition.
(I've seen this before)
'novel cause' is the wordplay.
'novel' indicates anagramming the letters.
'cause' with letters rearranged gives 'SAUCE'.
(Other definitions for sauce that I've seen before include "It's good for the goose and gander" , "Lip; foodstuff" , "Impertinence; dressing" , "Accompaniment to meat ect" , "Relish - impudence" .)