Vehicle turning up to meet plane containing Canada's foremost citizen (7)
I believe the answer is:
subject
'citizen' is the definition.
(I've seen this before)
'vehicle turning up to meet plane containing canada's foremost' is the wordplay.
'vehicle' becomes 'bus' (bus is a kind of vehicle).
'turning up' says the letters should be written in reverse.
'to meet plane' becomes 'jet' (I can't justify this - if you can you should believe this answer much more).
'containing' is an insertion indicator.
'foremost' suggests taking the first letters.
The first letter of 'canadas' is 'c'.
'bus' written backwards gives 'sub'.
'jet' placed around 'c' is 'ject'.
'sub'+'ject'='SUBJECT'
(Other definitions for subject that I've seen before include "One owing allegiance to monarch" , "Citizenship' at school maybe" , "Expose; field of study" , "One is under the authority of royalty" , "Topic - branch of study - citizen" .)