Gong finally sounded, interrupting dinner, say (5)
I believe the answer is:
medal
'gong' is the definition.
(I've seen this before)
'finally sounded interrupting dinner say' is the wordplay.
'finally' suggests the final letters.
'interrupting' means one lot of letters goes inside another.
'dinner say' becomes 'meal' (dinner is a kind of meal).
The last letter of 'sounded' is 'd'.
'd' placed inside 'meal' is 'MEDAL'.
(Other definitions for medal that I've seen before include "Commemorative piece of metal" , "Decorative award" , "Award for distinction" , "Prize; sounds like interfere" , "Military award" .)