Small flat sort of poker with one ring (6)
I believe the answer is:
studio
'small flat' is the definition.
'sort of poker with one ring' is the wordplay.
'sort of poker' becomes 'stud' (stud poker).
'with' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'ring' becomes 'o'.
'stud'+'i'+'o'='STUDIO'
(Other definitions for studio that I've seen before include "TV room?" , "Artist's workroom - film company" , "Workroom of an artist or photographer" , "Centre for movie-making" , "RA's workroom" .)