Release call for peace by superpower (7)

I believe the answer is:

quietus

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

'release call' is the definition.
'quietus' can be an answer for 'release' (thesaurus). I'm not sure about the 'call' bit.

'for peace by superpower' is the wordplay.
'for peace' becomes 'quiet' (I can't justify this - if you can you should believe this answer much more).
'by' means one lot of letters go next to another.
'superpower' becomes 'US' (the United States is a global superpower).
'quiet'+'us'='QUIETUS'

Can you help me to learn more?

(Other definitions for quietus that I've seen before include "Extinction, death" , "Final riddance - not quite quite us" , "Curtains" , "passing away" , "discharge" .)

I've seen this clue in The Guardian.

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.