Criminal in dirtiest gang is collapsing (14)

I believe the answer is:

disintegrating

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'collapsing' is the definition.
The definition and answer can be both related to change as well as being present participle verbs.
Maybe they are linked in a way I don't understand?

'criminal in dirtiest gang' is the wordplay.
'criminal' indicates an anagram.
'in'+'dirtiest'+'gang'='indirtiestgang'
'indirtiestgang' is an anagram of 'DISINTEGRATING'.

'is' acts as a link.

Can you help me to learn more?

(Another definition for disintegrating that I've seen is " breaking up".)

I've seen this clue in The Times.

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