Trendy revolutionary dropped by friendly set (7)

I believe the answer is:

congeal

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'set' is the definition.
(I know that set can be written as congeal)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for congeal that I've seen before include "Become semi-solid like cooling grease" , "Become gelatinous" , "Set - go clean (anag)" , "Clot" , "Coagulate" .)

I've seen this clue in The Sunday Times and The Times.

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