Northern dialect most Scots use (6)
I believe the answer is:
scouse
'northern dialect' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'most scots use' is the wordplay.
'most' means to remove the last letter.
'scots' becomes 'Scot' (synonyms).
'scot' with its final letter removed is 'sco'.
'sco'+'use'='SCOUSE'
Can you help me to learn more?
(Other definitions for scouse that I've seen before include "Liverpudlian (stew)" , "What they speak in Liverpool?" , "Liverpool accent" , "English dialect spoken in Liverpool" , "Liverpudlian (colloq.)" .)