Confirm it's just like being certain (6)

I believe the answer is:

assure

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

'just like being certain' is the wordplay.
'just like' becomes 'as' (I am not sure about the 'just' bit.).
'being certain' becomes 'sure' (synonyms).
'as'+'sure'='ASSURE'

'it's' acts as a link.

Can you help me to learn more?

(Other definitions for assure that I've seen before include "Make (something) certain to happen" , "Declare confidently, promise" , "Give confidence to" , "Cover by life insurance" , "Guarantee, promise" .)

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

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