Rep's odd sprees inside parlour (11)
I believe the answer is:
salesperson
'rep's' is the definition.
(as in a sales representative)
'odd sprees inside parlour' is the wordplay.
'odd' indicates anagramming the letters.
'inside' means one lot of letters goes inside another.
'parlour' becomes 'salon' (salon is a kind of parlour).
'sprees' anagrammed gives 'espers'.
'espers' going into 'salon' is 'SALESPERSON'.
(Other definitions for salesperson that I've seen before include "One must try to improve business" , "Shop server" , "Commercial traveller possibly" , "Shop attendant" , "Retail worker" .)