So-called ‘best insole’ stinking (10)

I believe the answer is:

ostensible

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'so-called' is the definition.
(thesaurus)

'best insole stinking' is the wordplay.
'best insole' can be anagrammed to 'OSTENSIBLE'.
However, I'm not sure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for ostensible that I've seen before include "Professed" , "Apparently true" , "Supposed" , "Apparent" , "Seeming" .)

I've seen this clue in The Everyman puzzle in The Observer.

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