Teen ran to rejoin gaudy swimmer (4,5)

I believe the answer is:

neon tetra

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

'gaudy swimmer' is the definition.
I don't know anything about this answer so I can't judge whether this works.

'teen ran to rejoin' is the wordplay.
'rejoin' indicates anagramming the letters (I've seen 'rejoined' mean this).
'teen'+'ran'+'to'='teenranto'
'teenranto' is an anagram of 'NEON TETRA'.

Can you help me to learn more?

(Other definitions for neon tetra that I've seen before include "Small iridescent fish" , "Iridescent tropical fish" .)

I've seen this clue in the Sydney Morning Herald.

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.