Someone who gives you drive in car without current tax (9)
I believe the answer is:
motivator
'someone who gives you drive' is the definition.
(a motivator drives people on)
'car without current tax' is the wordplay.
'car' becomes 'motor' (motor can informally mean a car).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'current' becomes 'I' (physics symbol).
'tax' becomes 'VAT' (UK Value Added Tax).
'i'+'vat'='ivat'
'motor' enclosing 'ivat' is 'MOTIVATOR'.
'in' is the link.
(Other definitions for motivator that I've seen before include "Person driving" , "Inspirer of others to action" .)