Has to be old-fashioned (4)

I believe the answer is:

hath

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I'm afraid I can't even guess how this answer relates to the clue.

(Other definitions for hath that I've seen before include "'The moon . . . . raised her lamp above' (The Lily of Killarney)" , "Has old" , "Has in an old-fashioned way" .)

I've seen this clue in the Evening Standard.

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