Vehicle going back into the ancient land (6)
I believe the answer is:
thrace
'ancient land' is the definition.
(I've seen this before)
'vehicle going back into the' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'going back' is a reversal indicator.
'into' means one lot of letters goes inside another.
'car' reversed gives 'rac'.
'rac' going within 'the' is 'THRACE'.
(Other definitions for thrace that I've seen before include "old part of Europe" , "Ancient region now in Greece and Bulgaria" , "Region of SE Balkans" , "The car (anag.); historical region" , "Historic region of SE Europe" .)