Crossword Genius

Out of tune, this tenor most sharp (9)

Ross

I believe the answer is:

thorniest

'most sharp' is the definition.

'out of tune this tenor' is the wordplay.
'out of tune' is an anagram indicator.
'this'+'tenor'='thistenor'
'thistenor' with letters rearranged gives 'THORNIEST'.

(Other definitions for thorniest that I've seen before include "Most troublesome or prickly" , "most problematic" .)

I've seen this clue in The Guardian.
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