Gong heard finally interrupting dinner? (5)
I believe the answer is:
medal
'gong' is the definition.
(gong can mean a prize or medal)
'heard finally interrupting dinner?' is the wordplay.
'finally' suggests the final letters.
'interrupting' means one lot of letters goes inside another.
'dinner?' becomes 'meal' (dinner is a kind of meal).
The last letter of 'heard' is 'd'.
'd' inserted within 'meal' is 'MEDAL'.
(Other definitions for medal that I've seen before include "Piece of metal as award or in commemoration" , "Metal disc awarded as prize, say in Olympics" , "Lamed (anag)" , "Award for achievement" , "Small metal disc as reward or prize" .)