Lady dines out showing gluttony? (6,3)
I believe the answer is:
deadly sin
'gluttony?' is the definition.
(gluttony is a kind of deadly sin)
'lady dines out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'lady'+'dines'='ladydines'
'ladydines' anagrammed gives 'DEADLY SIN'.
'showing' is the link.
(Other definitions for deadly sin that I've seen before include "Lethal lapse like pride, gluttony or envy" , "Eg, lust or gluttony" , "Greed, perhaps" , "greed, or lust" , "Anger, say" .)