Most secretive as this Lette cryptic (11)

I believe the answer is:

stealthiest

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'most secretive' is the definition.
Both the definition and answer are superlative adjectives. Perhaps they are linked in a way I don't understand?

'as this lette cryptic' is the wordplay.
'cryptic' indicates anagramming the letters (a cryptic or obscure order of the letters).
'as'+'this'+'lette'='asthislette'
'asthislette' anagrammed gives 'STEALTHIEST'.

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I've seen this clue in The Independent.

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