Catch some erring husbands (3)

I believe the answer is:

nab

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'catch' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for nab that I've seen before include "Cop" , "Catch; grab suddenly" , "Catch (thief) (colloq.)" , "Collar (sl.)" , "Pinch" .)

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