Sure to be specific? (7)

I believe the answer is:

certain

This clue is a double definition.

'sure' is the first definition.
(I know that sure can be written as certain)

'be specific' is the second definition.
(thesaurus)

'to' is the link.

(Other definitions for certain that I've seen before include "Proved beyond doubt" , "Indisputable" , "Assured" , "Absolutely sure" , "Convinced" .)

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

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