Unknown acid so misrepresented in circular diagrams (7)

I believe the answer is:

zodiacs

'circular diagrams' is the definition.
(I've seen this in another clue)

'unknown acid so misrepresented' is the wordplay.
'unknown' becomes 'z' (algebra).
'misrepresented' is an anagram indicator.
'acid'+'so'='acidso'
'acidso' is an anagram of 'odiacs'.
'z'+'odiacs'='ZODIACS'

'in' acts as a link.

(Another definition for zodiacs that I've seen is " sets of 12".)

I've seen this clue in The Guardian.

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