Pointless, giving up one’s commercial vehicle (3)
I believe the answer is:
van
'commercial vehicle' is the definition.
(I've seen this before)
'pointless giving up one's' is the wordplay.
'pointless' becomes 'vain' (I've seen this in another clue).
'giving up' suggests deleting specific letters.
'one' becomes 'i' (Roman numeral).
'vain' with 'i' taken away is 'VAN'.
(Other definitions for van that I've seen before include "Commercial vehicle or front of army" , "Goods vehicle" , "Trade vehicle" , "Delivery vehicle" , "Truck with an enclosed cargo space" .)