Crossword Genius

Fanatic has seconds of quality treat (5)

Ross

I believe the answer is:

ultra

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

'fanatic' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for ultra that I've seen before include "Over the top" , "Fanatic" , "Violet's predecessor" , "such sound treatment?" , "Secret intelligence" .)

I've seen this clue in the Sydney Morning Herald.
Want a hint initially instead of a full solution? Install my app