Bare arse inscribed with record number of sit-ups, say (4)
I believe the answer is:
reps
'number of sit-ups say' is the definition.
I can't judge whether this definition defines the answer.
'bare arse inscribed with record' is the wordplay.
'bare arse' becomes 'rs' (I can't explain this - if you can you should believe this answer much more).
'inscribed with' is an insertion indicator (I've seen this in other clues).
'record' becomes 'EP' (abbreviation for extended play record).
'rs' going around 'ep' is 'REPS'.
Can you help me to learn more?
(Other definitions for reps that I've seen before include "Salesman, in short" , "Travelling salespeople, in short" , "Travelling salesmen" , "Salesmen, in short" , "Agents" .)