Crossword Genius

Smash hit -- actress is most stiff (10)

Ross

I believe the answer is:

starchiest

'most stiff' is the definition.
('starchy' can be a synonym of 'stiff')

'smash hit actress' is the wordplay.
'smash' indicates anagramming the letters.
'hit'+'actress'='hitactress'
'hitactress' is an anagram of 'STARCHIEST'.

'is' is the link.

I've seen this clue in The Guardian.
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