Vehicle required for advancement? (3)
I believe the answer is:
van
'vehicle' is the definition.
(type of vehicle)
'required for advancement?' is the wordplay.
'required for' says the answer is hidden in the clue.
'VAN' is hidden within 'advancement'.
(Other definitions for van that I've seen before include "Light vehicle" , "Goods vehicle" , "Commercial vehicle at head of army" , "Trade vehicle" , "trailer" .)