A politician in the streets form impressions (6)

I believe the answer is:

stamps

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'impressions' is the definition.
(I know this)

'a politician in the streets form' is the wordplay.
'politician' becomes 'MP' (Member of Parliament).
'in the' is an insertion indicator.
'streets form' becomes 'sts' (I am not sure about this - if you are sure you should believe this answer much more).
'a'+'mp'='amp'
'amp' placed within 'sts' is 'STAMPS'.

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(Other definitions for stamps that I've seen before include "Brings foot down heavily onto the ground" , "Tokens stuck on letters" , "Puts the foot down on letters" , "Imprints" , "Gummed receipts of postal fees" .)

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

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