Month in America, below zero (5)

I believe the answer is:

minus

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

'month in america' is the wordplay.
'month' becomes 'm' (standard abbreviation).
'america' becomes 'us' (abbreviation for the United States).
'm'+'in'+'us'='MINUS'

(Other definitions for minus that I've seen before include "(Of temperature) below zero" , "Less, without" , "Negative sign - negative thing" , "'Take away' sign" , "Disadvantage" .)

I've seen this clue in The Telegraph.

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