One's paid rugby player to scratch bottom (3)
I believe the answer is:
pro
'one's paid' is the definition.
I can't tell whether this definition defines the answer.
'rugby player to scratch bottom' is the wordplay.
'rugby player' becomes 'prop' (type of rugby player).
'to scratch bottom' means to remove the last letter (I've seen 'scratching bottom' mean this).
'prop' with its final letter taken off is 'PRO'.
Can you help me to learn more?
(Other definitions for pro that I've seen before include "Of argument, say, in favour of" , "Golf expert" , "Skilled" , "Preposition meaning for, in favour of" , "Expert (abbr)" .)