A cat may be very nervous (4,7)

I believe the answer is:

have kittens

I believe this clue is a double definition.

'a cat may' is the first definition.
(a cat may have kittens)

'be very nervous' is the second definition.
(to have kittens is figuratively to be anxious)

(Other definitions for have kittens that I've seen before include "Shake with nerves" , "Blow up" , "produce cute delivery" , "Be extremely nervous (as a queen might)" .)

I've seen this clue in The Times.

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