In garret Lou found system controller (9)

I believe the answer is:

regulator

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

'controller' is the definition.
(I know that regulator is a type of controller)

'in garret lou found system' is the wordplay.
'garret lou' can be anagrammed to 'REGULATOR'.
However, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for regulator that I've seen before include "Supervisor" , "Of body" , "Controlling device" , "Governor" , "Such as OFGAS, OFTEL etc" .)

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

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