Cheek of son visiting famous regiment (4)

I believe the answer is:

sass

'cheek' is the definition.
(sass is a kind of cheek)

'son visiting famous regiment' is the wordplay.
'son' becomes 's'.
'visiting' is an insertion indicator.
'famous regiment' becomes 'sas' (Special Air Service).
's' placed within 'sas' is 'SASS'.

'of' acts as a link.

(Another definition for sass that I've seen is " Cheek".)

I've seen this clue in The Times.

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