Difference in volume from the magic flute in the back of church (8)
I believe the answer is:
variance
'difference' is the definition.
(variance is a kind of difference)
'volume from the magic flute in the back of church' is the wordplay.
'volume' becomes 'v'.
'from' says to put letters next to each other.
'the magic flute in' becomes 'naira' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'the back of' says the letters should be written backwards (I've seen 'back' mean this).
'church' becomes 'ce' (abbreviation for Church of England).
'naira' back-to-front is 'arian'.
'v'+'arian'+'ce'='VARIANCE'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for variance that I've seen before include "Change" , "Not the main attraction" , "Dissension" , "disagreement" , "Difference, discrepancy" .)