On which bums can be said to mean success in the theatre (5)
I believe the answer is:
seats
'success in the theatre' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'on which bums can be said to' is the wordplay.
I cannot quite see how this works, but
'on' could be 'at' (I've seen this in other clues) and 'at' is present in the answer.
The remaining letters 'ses' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'mean' is the link.
Can you help me to learn more?
(Other definitions for seats that I've seen before include "Chairs, stools" , "Parliamentary constituencies" .)