Sing, roar? Belt out of military base! (8)

I believe the answer is:

garrison

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

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

'sing roar? belt out' is the wordplay.
'sing roar' anagrams to 'GARRISON'.
However, I am not clear how this is indicated.

'of' acts as a link.

Can you help me to learn more?

(Other definitions for garrison that I've seen before include "(Soldiers stationed to guard) fortified place" , "Military base" , "army base?" , "HQ" , "Body of troops guarding a stronghold" .)

I've seen this clue in the Irish Times and the Irish Times (Crosaire).

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