Drive back westbound Underground passenger? (5)
I believe the answer is:
rebut
'drive back' is the definition.
(I've seen this before)
'westbound underground passenger?' is the wordplay.
'westbound' shows that the letters should be reversed in order (letters written from right to left).
'underground' becomes 'tube' ('tube' can be a synonym of 'underground').
'passenger?' becomes 'r' (I can't justify this - if you can you should give a lot more credence to this answer).
'tube'+'r'='tuber'
'tuber' backwards is 'REBUT'.
Can you help me to learn more?
(Other definitions for rebut that I've seen before include "show as bad" , "Brute can refute" , "Deny claim" , "Overturn" , "Disprove an accusation" .)