Fine for interrupting a game (5)
I believe the answer is:
poker
'game' is the definition.
(I know that poker is a card game)
'fine for interrupting a' is the wordplay.
'fine' becomes 'ok' (synonyms).
'for interrupting' means one lot of letters goes inside another.
'a' becomes 'per' (eg 'one a day' means 'one per day').
'ok' put inside 'per' is 'POKER'.
(Other definitions for poker that I've seen before include "Fire prod; game" , "Fire prodder; game" , "Card-game" , "See 1" , "Fire rod; game" .)