Ruin a French party (4)

I believe the answer is:

undo

'ruin' is the definition.
(I know that undo is a type of ruin)

'a french party' is the wordplay.
'a french' becomes 'un' ('a' in French).
'party' becomes 'do' (do is a kind of party).
'un'+'do'='UNDO'

(Other definitions for undo that I've seen before include "Subvert" , "(4)" , "Open, a knot say" , "Dismantle - destroy" , "Unfasten or annul" .)

I've seen this clue in The Telegraph, The Times, The Everyman puzzle in The Observer, The Independent and The Globe and Mail.

Want a hint initially instead of a full solution? Install my app