Most lean and sinewy form of grittiness (10)

I believe the answer is:

stringiest

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'most lean' is the definition.
('stringy' can be similar in meaning to 'lean')

'sinewy form of grittiness' is the wordplay.
'grittiness' anagrams to 'STRINGIEST'.
However, I am not sure how this is indicated.

'and' acts as a link.

Can you help me to learn more?

I've seen this clue in The Telegraph.

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