It's a mystery to flipping Russell consuming top malt spirit? (6)
I believe the answer is:
enigma
'it's a mystery' is the definition.
('enigma' can be a synonym of 'mystery')
'to flipping russell consuming top malt spirit?' is the wordplay.
'to flipping' is a reversal indicator.
'russell' becomes 'ae' (I can't justify this - if you can you should give a lot more credence to this answer).
'consuming' is an insertion indicator.
'top' indicates taking the first letters.
'spirit?' becomes 'gin' (I've seen this before).
The initial letter of 'malt' is 'm'.
'm'+'gin'='mgin'
'ae' going around 'mgin' is 'amgine'.
'amgine' back-to-front is 'ENIGMA'.
Can you help me to learn more?
(Other definitions for enigma that I've seen before include "WW2 code" , "Conundrum" , "Elgar Variations nickname" , "Gamine being a bit of a puzzle" , "Puzzle found in gem, Ian" .)