In the circumstances, blackguard reaches waterfall (7)

I believe the answer is:

cascade

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'waterfall' is the definition.
(synonyms)

'in the circumstances blackguard' is the wordplay.
'in the' is an insertion indicator.
'circumstances' becomes 'case' (I can't justify this - if you can you should believe this answer much more).
'blackguard' becomes 'cad' (both can mean a dishonourable person).
'case' enclosing 'cad' is 'CASCADE'.

'reaches' is the link.

Can you help me to learn more?

(Other definitions for cascade that I've seen before include "Shower" , "Tumble down (like water)" , "Sudden downpour" , "Torrent" , "Waterfall or deluge" .)

I've seen this clue in The Irish News.

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