Saucer-shaped instrument (4)
I believe the answer is:
gong
'saucer-shaped instrument' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gong that I've seen before include "Dinner call - medal" , "Medal; forty down" , "Beat this" , "Sound announcing meal" , "Dinner bell or slang medal" .)