Sound of policeman thundered around walls of tenement (6-8)

'sound' is the definition.
(both can mean reliable)

'policeman thundered around walls of tenement' is the wordplay.
I cannot quite understand how this works, but
'policeman' could be 'copper' (copper can informally mean a police officer) and 'copper' is found in the answer.
'around' could be 'o' (a round letter) and 'o' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

'of' acts as a link.

Can you help me to learn more?