He's mastered the art of eating out (6)
I believe the answer is:
etcher
'he's mastered the art of eating out' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he's mastered the' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
'he' could be 'che' and 'che' is found in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for etcher that I've seen before include "Artist such as Rembrandt" , "Engraver" , "Artist who likes to make an impression?" , "One making an impression" , "Creative artist" .)