Westwards advance in second vehicle (7)
I believe the answer is:
omnibus
'vehicle' is the definition.
(I've seen this before)
'westwards advance in second' is the wordplay.
'westwards' shows that the letters should be reversed in order (letters go right to left or from 'east' to 'west').
'advance' becomes 'sub' (both can mean a loan).
'second' becomes 'mo' (both are short periods of time).
'sub'+'in'+'mo'='subinmo'
'subinmo' written backwards gives 'OMNIBUS'.
(Other definitions for omnibus that I've seen before include "Large volume - public transport" , "Collection of writings" , "Collection of writing" , "One progresses by stages" , "Large vehicle - collected edition" .)