he cursed endlessly, unravelling with no less depravity - (13)

I believe the answer is:

lecherousness

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'depravity' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

'he cursed endlessly unravelling with no less' is the wordplay.
'endlessly' means to remove the last letter.
'unravelling with' is an anagram indicator.
'he'+'cursed'='hecursed'
'hecursed' with its last letter taken away is 'hecurse'.
'no'+'less'='noless'
'hecurse' anagrammed with 'noless' can make 'LECHEROUSNESS'.

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