Sound elements of local brass on top ten (5)
I believe the answer is:
audio
'sound' is the definition.
(audio means sound)
'elements of local brass on top ten' is the wordplay.
'elements of local brass' becomes 'aud' (I can't explain this - if you can you should give a lot more credence to this answer).
'on top' means one lot of letters go next to another (in a down clue, some letters go above others).
'ten' becomes 'IO' (IO resembles a0).
'aud'+'io'='AUDIO'
Can you help me to learn more?
(Other definitions for audio that I've seen before include "Recording of acoustic signals" , "What is heard" , "Prefix indicating hearing or sound" , "- - visual aids" , "Reproduction of recorded sound" .)