First-class sort of voting idea regularly netting millions (5)
I believe the answer is:
prime
'first-class' is the definition.
(I've seen this in another clue)
'sort of voting idea regularly netting millions' is the wordplay.
'sort of voting' becomes 'pr' (I can't explain this - if you can you should believe this answer much more).
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'netting' is an insertion indicator (net can mean to contain or capture).
'millions' becomes 'm' (abbreviation).
The alternating letters of 'idea' are 'ie'.
'ie' placed around 'm' is 'ime'.
'pr'+'ime'='PRIME'
Can you help me to learn more?
(Other definitions for prime that I've seen before include "Brief" , "At least two" , "Foremost" , "Main; make usable" , "Monastic service; best quality" .)