Left, say, not as much plastered (7)
I believe the answer is:
legless
'plastered' is the definition.
(I know that plastered can be written as legless)
'left say not as much' is the wordplay.
'left say' becomes 'leg' (left leg).
'not as much' becomes 'less' (similar in meaning).
'leg'+'less'='LEGLESS'
(Other definitions for legless that I've seen before include "Tight" , "Informally drunk, lacking nether limbs" , "So one couldn't stand" , "hammered" , "Brahms and Liszt" .)