Traveller could give harangue following plane (7)
I believe the answer is:
migrant
'traveller' is the definition.
(I know that migrant is a type of traveller)
'harangue following plane' is the wordplay.
'harangue' becomes 'rant' (synonyms).
'following' means one lot of letters go next to another.
'plane' becomes 'mig' (fighter jet produced by Russian company MiG).
'rant' put after 'mig' is 'MIGRANT'.
'could give' is the link.
(Other definitions for migrant that I've seen before include "Person moving abroad" , "Ring mat (anag.)" , "Changing habitat (bird)" , "one leaving the country" , "Traveller" .)