Soldiers sing and roar riotously (8)
I believe the answer is:
'soldiers sing and roar riotously' is the definition.
I can't judge whether this defines the answer.
'sing and roar riotously' is the wordplay.
'and' means one lot of letters go next to another.
'riotously' indicates an anagram.
'sing' after 'roar' is 'roarsing'.
'roarsing' with letters rearranged gives 'GARRISON'.
Can you help me to learn more?
(Other definitions for garrison that I've seen before include "Roarings (anag.)" , "Military fortress" , "troops in base" , "Troops defending a town or fortress" , "Military fort" .)