Stewed lamb, say, is awful (7)
I believe the answer is:
abysmal
'awful' is the definition.
(I've seen this before)
'stewed lamb say' is the wordplay.
'stewed' indicates anagramming the letters.
'lamb'+'say'='lambsay'
'lambsay' with letters rearranged gives 'ABYSMAL'.
'is' is the link.
(Other definitions for abysmal that I've seen before include "Extreme and deplorable, perhaps ignorance" , "Very bad or bottomless" , "Very bad, poor" , "Very bad or limitless" , "Very bad indeed" .)