Jack from Ontario (3)

I believe the answer is:

tar

'jack' is the definition.
(thesaurus)

'from ontario' is the wordplay.
'from' indicates a hidden word.
'TAR' can be found hidden inside 'ontario'.

(Other definitions for tar that I've seen before include "Sailor (colloq.)" , "Flammable liquid; sailor" , "Product of coal" , "Dark viscid substance" , "Slang sailor or road surfacing material" .)

I've seen this clue in the Evening Standard.

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