Fish vessel useful to motorists (3,4)

I believe the answer is:

car park

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'useful to motorists' is the definition.
I can't judge whether this defines the answer.

'fish vessel' is the wordplay.
'fish' becomes 'carp' (carp is a kind of fish).
'vessel' becomes 'ark' (ark is a kind of vessel).
'carp'+'ark'='CAR PARK'

Can you help me to learn more?

(Other definitions for car park that I've seen before include "Where vehicles are left" , "of which many stories might be told" , "designated area" , "place with many bays" , "Multi-storey building with bays" .)

I've seen this clue in the Evening Standard.

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