Player earning roubles invested with Italian banker (3)
I believe the answer is:
pro
'player earning' is the definition.
(professional player as opposed to amateur)
'roubles invested with italian banker' is the wordplay.
'roubles' becomes 'r'.
'invested with' is an insertion indicator.
'italian banker' becomes 'po' (Italian river, something that 'banks').
'r' placed into 'po' is 'PRO'.
(Other definitions for pro that I've seen before include "gets paid to play?" , "Paid worker" , "Top player" , "With qualifications" , "Prefix meaning for" .)