Bad to leave without wife (3)

I believe the answer is:

ill

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'bad' is the definition.
(similar in meaning)

I don't understand how the rest of the clue works.

(Other definitions for ill that I've seen before include "In a bad way" , "'Never speak . . . of the dead'" , "Not well, sick" , "Dicky" , "laid up?" .)

I've seen this clue in The Times.

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