Delia's perfect form (5)

I believe the answer is:

ideal

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'perfect form' is the definition.
'ideal' can be an answer for 'perfect' (I've seen this in another clue). I am unsure of the 'form' bit.

'delia's' is the wordplay.
'delia' anagrams to 'IDEAL'.
But, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for ideal that I've seen before include "just the job" , "Most suitable" , "Perfect but not likely to become a reality" , "(the best one can get)" , "without a flaw" .)

I've seen this clue in The Globe and Mail, The Irish Independent and The Irish News.

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