Number two failing (4)

I believe the answer is:

vice

I believe this is a double definition.

'number two' is the first definition.
(eg vice-president)

'failing' is the second definition.
(I've seen this in other clues)

(Other definitions for vice that I've seen before include "Getting a grip" , "Prefix for deputy to, say, chairman" , "something antisocial" , "Sin, depravity" , "Bad habits" .)

I've seen this clue in The Guardian.

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