Gregory's own self (3)
I believe the answer is:
ego
'self' is the definition.
(synonyms)
'gregory's own' is the wordplay.
'EGO' is hidden in amongst the letters.
However, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for ego that I've seen before include "One's sense of self-importance" , "One's self image" , "See 21 Down" , "One's image of oneself" , "Sense of self, conceit" .)