Irish sound mischievous, British superior (6)
I believe the answer is:
brogue
'irish sound mischievous british superior' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'british superior' is the wordplay.
I cannot really see how this works, but
'british' could be 'br' (abbreviation for British) and 'br' is found in the answer.
'superior' could be 'u' (U can mean upper-class, as in U and non-U speech) and 'u' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for brogue that I've seen before include "Thick and heavy shoe" , "Irish or Scottish accent?" , "Irish accent or strong shoe" , "Style of shoe - style of accent" , "afoot?" .)