A common swimmer, termed “coarse” (5)

I believe the answer is:

roach

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

'a common swimmer' is the definition.
'roach' can be an answer for 'swimmer' (roach is a kind of fish). I am unsure of the 'a common' bit.

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for roach that I've seen before include "Silvery freshwater fish" , "joint near the end" , "Small freshwater fish related to carp" , "Fresh-water food fish" , "Something fishy here" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.