Top criminal Russian fighter accepting bribe on a regular basis (2,3)
I believe the answer is:
mr big
'top criminal russian' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'fighter accepting bribe on a regular basis' is the wordplay.
'fighter' becomes 'mig' (I've seen this in other clues).
'accepting' is an insertion indicator.
'on a regular basis' indicates alternate letters.
The alternate letters of 'bribe' are 'rb'.
'mig' enclosing 'rb' is 'MR BIG'.
Can you help me to learn more?
(Other definitions for mr big that I've seen before include "Important man" , "boss" , "chief" , "Top man" .)