Commercial traveller (8)
I believe the answer is:
salesman
'commercial traveller' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for salesman that I've seen before include "Travelling rep" , "He's a seller" , "Arthur Miller wrote 'Death of a . . . . . . . .'" , "He sells strange lean mass" , "Fermented honey drink" .)