Fish on river or one on ice, perhaps (6)
I believe the answer is:
skater
'ice perhaps' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'fish on river or one' is the wordplay.
I cannot really understand how this works, but
'fish' could be 'skate' (skate is a kind of fish) and 'skate' is found in the answer.
'river' could be 'r' (abbreviation for river) and 'r' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'on' is the link.
Can you help me to learn more?
(Other definitions for skater that I've seen before include "Could one roll up" , "Athlete on blades" , "Winter sportsman" , "Streak (anag)" , "One sliding over ice" .)