Damaging trespass is most infrequent (8)

I believe the answer is:

sparsest

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'most infrequent' is the definition.
Both the definition and answer are superlative adjectives. Maybe there's an association between them I don't understand?

'damaging trespass' is the wordplay.
'damaging' indicates anagramming the letters.
'trespass' anagrammed gives 'SPARSEST'.

'is' is the link.

Can you help me to learn more?

(Another definition for sparsest that I've seen is " Most scattered".)

I've seen this clue in The Guardian.

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