Overhaul salesman's appearance (6)
I believe the answer is:
repair
'overhaul' is the definition.
(thesaurus)
'salesman's appearance' is the wordplay.
'salesman' becomes 'rep' (I've seen this before).
'appearance' becomes 'air' (I've seen this before).
'rep'+'air'='REPAIR'
(Other definitions for repair that I've seen before include "Correct" , "Mend - go" , "Make good again" , "Proceed - restore" , "Restore (something) to good condition" .)