Single occupant of the setter's capital (5)
I believe the answer is:
money
'capital' is the definition.
(thesaurus)
'single occupant of the setter's' is the wordplay.
I cannot really see how this works, but
'single' could be 'one' (similar in meaning) and 'one' is found in the answer.
'setter's' could be 'my' (belonging to the crossword setter) and 'my' is present in the leftover letters.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for money that I've seen before include "Bread" , "Mazuma, ackers or dosh" , "It's the root of all evil" , "ready" , "See 7" .)