Crossword Genius

Runs after large fish one moves on wheels (6)

Ross

I believe the answer is:

skater

I'm a little stuck... Click here to teach me more about this clue!

'moves on wheels' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'runs after large fish one' is the wordplay.
I cannot quite understand how this works, but
'runs' could be 'r' (cricket abbreviation) and 'r' is found within the answer.
'fish' could be 'skate' (skate is a kind of fish) and 'skate' is located in the answer.
No letters remain.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for skater that I've seen before include "Winter sports person" , "Athlete on blades" , "Winter sports participant" , "Mover across ice" , "Ice sportsman" .)

I've seen this clue in The Times.
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