Musical piece about a quirk of knowledge (7)
I believe the answer is:
gnostic
'musical piece about a quirk of knowledge' is the definition.
I can't tell whether this defines the answer.
'musical piece about a quirk' is the wordplay.
'musical piece' becomes 'song' (song is a kind of piece. I am not sure about the 'musical' bit.).
'about' says the letters should be written in reverse.
'a quirk' becomes 'tic' (I've seen this in another clue).
'song' back-to-front is 'gnos'.
'gnos'+'tic'='GNOSTIC'
Can you help me to learn more?
(Other definitions for gnostic that I've seen before include "Occult" , "Relating to mystical knowledge" , "Having special mystical knowledge, costing a lot" .)