I only trade in perfection (5)

I believe the answer is:

ideal

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

'perfection' is the definition.
(I've seen this before)

'i only trade' is the wordplay.
'only trade' becomes 'deal' (synonyms. I am not sure about the 'only' bit.).
'i'+'deal'='IDEAL'

'in' acts as a link.

Can you help me to learn more?

(Other definitions for ideal that I've seen before include "fanciful" , "Model of perfection" , "Standard of perfection or excellence" , "Perfectly suited" , "Coal-mining waste" .)

I've seen this clue in the Evening Standard.

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