Smart, salesman dressing up (6)
I believe the answer is:
dapper
'smart' is the definition.
(I've seen this before)
'salesman dressing up' is the wordplay.
'salesman' becomes 'rep' (sales representative).
'dressing' becomes 'pad' (type of medical dressing).
'up' is a reversal indicator (in down clue: letters go upwards).
'rep'+'pad'='reppad'
'reppad' in reverse letter order is 'DAPPER'.
(Other definitions for dapper that I've seen before include "Well turned out" , "Smartly dressed" , "Neat and smart in appearance" , "Neat and trim in dress" , "Of man, neat and smart" .)