Going over part of Glinka score (3)
I believe the answer is:
nil
'score' is the definition.
(I've seen this before)
'going over part of glinka' is the wordplay.
'going over' says the letters should be written backwards.
'part of' indicates a hidden word.
'lin' is hidden in the letters of 'glinka'.
'lin' in reverse letter order is 'NIL'.
(Other definitions for nil that I've seen before include "There's nothing left" , "Latin zero" , "Nothing, no value" , "Score of nought" , "Nothing, zero" .)