Passing itinerants heading off to work (9)
I believe the answer is:
transient
'passing' is the definition.
('transient' can be a synonym of 'passing')
'itinerants heading off to work' is the wordplay.
'heading off' means to remove the first letter.
'to work' is an anagram indicator.
'itinerants' with its first letter removed is 'tinerants'.
'tinerants' anagrammed gives 'TRANSIENT'.
(Other definitions for transient that I've seen before include "fugitive" , "Lasting a short time" , "Passing, short-lived" , "on the move" , "Ephemeral" .)