Lady, is drink good in place of mud pie? (11)
I believe the answer is:
mississippi
'place of mud pie?' is the definition.
(as in a Mississippi mud pie)
'lady is drink good' is the wordplay.
I cannot really understand how this works, but
'lady' could be 'issi' and 'issi' is located in the answer.
'drink' could be 'sip' (sipping is a kind of drinking) and 'sip' is found in the answer.
'good' could be 'pi' (old-fashioned term for pious) and 'pi' is found in the answer.
The remaining letters 'ms' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'in' acts as a link.
(Other definitions for mississippi that I've seen before include "US state, capital Jackson" , "So-called old man" , "American runner" , ""Old Man River"" , "US state, joined 1817" .)