Strengthen censor's noise obscuring "eff you" (4,2)

I believe the answer is:

beef up

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

'strengthen' is the definition.
(I know that strengthen can be written as beef up)

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for beef up that I've seen before include "buttress" , "Gain muscle" , "Reinforce (colloq.)" , "Add strength to" , "Give added strength" .)

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.