Crossword Genius

Open-air types will be out of these (5)

Ross

I believe the answer is:

doors

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

'open-air types' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Maybe there's an association between them I don't understand?

'out of these' is the wordplay.
I cannot quite see how this works, but
'of' could be 'o' and 'o' is found in the answer.
The remaining letters 'dors' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

'will be' is the link.

Can you help me to learn more?

(Other definitions for doors that I've seen before include "Openings" , "Swinging or sliding barriers" , "Barriers to entrances" , "Portals" , "Ways in and out" .)

I've seen this clue in The Globe and Mail.
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