Appropriate vehicle hired again outside (8)
I believe the answer is:
relevant
'appropriate' is the definition.
(I've seen this before)
'vehicle hired again outside' is the wordplay.
'vehicle' becomes 'van' (van is a kind of vehicle).
'hired again' becomes 'relet' (to re-let something can mean to hire it again).
'outside' is an insertion indicator.
'van' placed inside 'relet' is 'RELEVANT'.
(Other definitions for relevant that I've seen before include "Bearing on the issue in hand" , "Bearing upon the matter in hand" , "Significant" , "Appropriate" , "Closely connected (to the matter in hand)" .)