Thin circular object (4)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
disc
'thin circular object' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for disc that I've seen before include "jockey may be after" , "Sound recording" , "Back part" , "Circle" , "Body without limbs" .)