Basic quality of flat beyond the doorway (5,5)
I believe the answer is:
entry-level
'basic quality' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'flat beyond the doorway' is the wordplay.
'flat' becomes 'level' ('level' can be a synonym of 'flat'**).
'beyond' is a charade indicator (letters next to each other).
'the doorway' becomes 'entry' ('entry' can be a synonym of 'doorway').
'level' after 'entry' is 'ENTRY-LEVEL'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for entry-level that I've seen before include "Simple enough for a beginner" , "Suitable for beginners" .)