Lodger one getting on transport (7)
I believe the answer is:
boarder
'lodger' is the definition.
(synonyms)
'one getting on transport' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'a' (a thing is one thing) and 'a' is found in the answer.
The remaining letters 'border' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for boarder that I've seen before include "Pupil living at school" , "Lodger - invader of boat" , "School liver-in" , "Tenant" , "one that's getting on plane" .)