Firm new angle to set firm (7)

I believe the answer is:

congeal

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'set firm' is the definition.
'congeal' can be an answer for 'set' (synonyms). I am unsure of the 'firm' bit.

'firm new angle' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'new' indicates an anagram.
'angle' is an anagram of 'ngeal'.
'co'+'ngeal'='CONGEAL'

'to' acts as a link.

Can you help me to learn more?

(Other definitions for congeal that I've seen before include "Jell" , "Become solid" , "Set - go clean (anag)" , "Solidify by cooling" , "Curdle" .)

I've seen this clue in the Sydney Morning Herald.

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