Accommodation on one level? (4)
I believe the answer is:
flat
This clue is a double definition.
'accommodation' is the first definition.
(thesaurus)
'one level?' is the second definition.
(thesaurus)
'on' is the link.
(Other definitions for flat that I've seen before include "Quarters - punctured - smooth" , "Like a pancake?" , "Dull; apartment" , "lacking in taste" , "Unnatural - uninteresting - apartment" .)