Vehicle difficult to get out of? (4)

I believe the answer is:

trap

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'vehicle' is the definition.
(trap is a kind of vehicle)

I cannot understand how the rest of the clue works.

(Other definitions for trap that I've seen before include "The Web" , "Light carriage; ensnare" , "Gin - hidden danger" , "Control ball" , "Snare - mouth" .)

I've seen this clue in the Evening Standard.

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