This month in Westminster (4)

I believe the answer is:

inst

'this month' is the definition.
(letter-writing abbreviation for this month)

'in westminster' is the wordplay.
'in' says the answer is hidden in the clue.
'INST' is hidden within 'westminster'.

(Other definitions for inst that I've seen before include "Be sorry for" , "Business notation for the current month" , "Present month (on business letters)" , "Present month (abbrev.)" , "Abbreviation for this month in business correspondence" .)

I've seen this clue in The Globe and Mail.

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