My French upset commercial traveller (5)
I believe the answer is:
nomad
'traveller' is the definition.
(I know that nomad is a type of roamer)
'my french upset commercial' is the wordplay.
'my french' becomes 'mon' ('my' in French).
'upset' says the letters should be written in reverse.
'commercial' becomes 'ad' (abbreviation for advertisement).
'mon' back-to-front is 'nom'.
'nom'+'ad'='NOMAD'
(Other definitions for nomad that I've seen before include "Rover" , "Unsettled character" , "drifter" , "Person always on the move" , "someone who can't settle" .)