Round roof includes, for eccentric artist, a way in (9)

I believe the answer is:

doorframe

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'a way in' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'round roof includes for eccentric artist' is the wordplay.
'round roof' becomes 'dome' (I've seen this in another clue).
'includes' means one lot of letters goes inside another.
'eccentric' is an anagram indicator.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'for' anagrammed gives 'orf'.
'orf'+'ra'='orfra'
'dome' enclosing 'orfra' is 'DOORFRAME'.

Can you help me to learn more?

(Another definition for doorframe that I've seen is " Architrave".)

I've seen this clue in The Daily Express.

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