Firm reservations arranged for rooms on ground floor (14)

I believe the answer is:

conservatories

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'rooms on ground floor' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Maybe they are linked in a way I don't understand?

'firm reservations arranged' is the wordplay.
'firm' becomes 'co' (a firm is a company**).
'arranged' indicates anagramming the letters.
'reservations' is an anagram of 'nservatories'.
'co'+'nservatories'='CONSERVATORIES'

'for' is the link.

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I've seen this clue in The Times.

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