Business scaling fry up? (5,4)

I believe the answer is:

trout farm

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

'business' is the definition.
(I have seen 'fishy business' mean 'trout farm' so perhaps 'business' could also mean 'trout farm')

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for trout farm that I've seen before include "Where fish are bred" , "Commercial fish producer" , "Fish-rearing concern" , "river factory" , "fishy business" .)

I've seen this clue in The Telegraph.

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.