Design assists in production of cars (10)

I believe the answer is:

hatchbacks

'cars' is the definition.
(hatchback is a kind of car)

'design assists' is the wordplay.
'design' becomes 'hatch' (hatch is a kind of design).
'assists' becomes 'backs' (back can mean to support or assist).
'hatch'+'backs'='HATCHBACKS'

'in production of' is the link.

(Another definition for hatchbacks that I've seen is " vehicles".)

I've seen this clue in The Times.

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