A large painting done out of doors (8)

I believe the answer is:

alfresco

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'out of doors' is the definition.
(synonyms)

'a large painting' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'painting' becomes 'fresco' (fresco is a kind of painting).
'a'+'l'+'fresco'='ALFRESCO'

'done' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for alfresco that I've seen before include "Meal eaten in the outdoors" , "In the open air" , "Open-air" , "out of the house" , "Outdoors, meal perhaps" .)

I've seen this clue in The Times.

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