Caught skinny rat washing (9)

I believe the answer is:

cleansing

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'washing' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?

'caught skinny rat' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'skinny' becomes 'lean' (similar in meaning).
'rat' becomes 'sing' (both can mean to inform on someone).
'c'+'lean'+'sing'='CLEANSING'

Can you help me to learn more?

(Other definitions for cleansing that I've seen before include "Purging" , "Nice slang for making thoroughly free from dirt (9)" .)

I've seen this clue in The Telegraph.

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