Salesman performing ace routine (10)
I believe the answer is:
auctioneer
'salesman' is the definition.
(I know that auctioneer is a type of salesman)
'performing ace routine' is the wordplay.
'performing' is an anagram indicator (the letters move around or 'perform').
'ace'+'routine'='aceroutine'
'aceroutine' with letters rearranged gives 'AUCTIONEER'.
(Other definitions for auctioneer that I've seen before include "One selling lots" , "One inviting bids for lots" , "one that has lots to offer" .)