Gratified sufferer is stomach-churning (9)
I believe the answer is:
masochist
'gratified sufferer' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'is stomach-churning' is the wordplay.
'churning' is an anagram indicator.
'is'+'stomach'='isstomach'
'isstomach' is an anagram of 'MASOCHIST'.
Can you help me to learn more?
(Other definitions for masochist that I've seen before include "One who likes pain" , "deviant"" , "one enjoying humiliation" .)