Polo makes little difference to Mario (5)
I believe the answer is:
marco
This clue might be a double definition.
'polo' is the first definition.
(I've seen this in another clue)
'mario' is the second definition.
(I know that mario can be written as Marco)
'makes little difference to' acts as a link.
This may not be correct. Some or all of it may belong to one of the definitions.
Can you help me to learn more?
(Other definitions for marco that I've seen before include "gondolier" , "- - Polo, traveller" .)