Traveller that is carrying the can, getting harangue (9)
'traveller' is the definition.
(itinerant is a kind of traveller)
'that is carrying the can getting harangue' is the wordplay.
'that is' becomes 'ie' (synonyms).
'carrying' means one lot of letters goes inside another.
'the can' becomes 'tin' ('tin' can be a synonym of 'can').
'getting' is a charade indicator (letters next to each other).
'harangue' becomes 'rant' (synonyms).
'ie' enclosing 'tin' is 'itine'.
(Other definitions for itinerant that I've seen before include "Tie-in rant to a traveller", "Rambling", "Person who moves from place to place", "Moving from place to place", "Nomad".)