Parent wrong about principal form of sonnet (10)

I believe the answer is:

petrarchan

I'm a little stuck... Click here to teach me more about this clue!

'form of sonnet' is the definition.
'Petrarchan' can be an answer for 'sonnet' (Petrarchan sonnet is an example). I'm not sure about the 'form of' bit.

'parent wrong about principal' is the wordplay.
'wrong' indicates an anagram.
'about' indicates putting letters inside.
'principal' becomes 'arch' (as in arch-enemy).
'parent' is an anagram of 'petran'.
'petran' going around 'arch' is 'PETRARCHAN'.

Can you help me to learn more?

(Another definition for petrarchan that I've seen is " according to poet".)

I've seen this clue in The Times.

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