Introductions to duke, earl, judge and viscount use sense of repetition (4,2)
I believe the answer is:
deja vu
'sense of repetition' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'introductions to duke earl judge and viscount use' is the wordplay.
'introductions to' says to take the initial letters.
The first letters of 'duke earl judge and viscount use' is 'DEJA VU'.
Can you help me to learn more?
(Other definitions for deja vu that I've seen before include "Illusion that a new experience had occurred previously" , "Experience of feeling that we've been here before" , "Familiar feeling" , "The experience of thinking a new situation has happened before" , "Imagining one's repeating" .)