Dig popular ruler going two-thirds of the way? (6)
I believe the answer is:
insult
'dig' is the definition.
(dig can mean an insulting remark)
'popular ruler going two-thirds of the way?' is the wordplay.
I cannot really understand how this works, but
'popular' could be 'in' ('in' can mean trendy) and 'in' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'way?' could be 's' (Compass direction - South) and 's' is present in the answer.
This explanation may well be incorrect...
(Other definitions for insult that I've seen before include "Speak or act in way designed to hurt" , "An addition to injury?" , "Speak rudely or offensively about" , "Treat disrespectfully" , "Show contempt to" .)