Establish Riviera resort when one's neglected the French part (8)
I believe the answer is:
provence
'part' is the definition.
(I have seen 'part of France' mean 'provence' so perhaps 'part' could also mean 'provence')
'establish riviera resort when one's neglected the french' is the wordplay.
I cannot really see how this works, but
'establish' could be 'prove' (synonyms) and 'prove' is found in the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for provence that I've seen before include "Never cop this French region" , "somewhere in France" , "Region of southeast France" , "part of France" , "Area of SE France" .)