Crossword Genius

Fool includes certain guarantees (7)

Ross

I believe the answer is:

assures

'guarantees' is the definition.
('assure' can be a synonym of 'guarantee')

'fool includes certain' is the wordplay.
'fool' becomes 'ass' (ass is a kind of fool).
'includes' is an insertion indicator.
'certain' becomes 'sure' (synonyms).
'ass' going around 'sure' is 'ASSURES'.

(Other definitions for assures that I've seen before include "guarantees" , "States positively and confidently" , "Informs with certainty and confidence" , "Tells to dispel any doubts" , "Gives confidence or covers with a policy" .)

I've seen this clue in The Guardian.
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