Energy about a brass band's sound (6)
I believe the answer is:
oompah
'sound' is the definition.
(I have seen 'brassy sound' mean 'oompah' so perhaps 'sound' could also mean 'oompah')
'energy about a brass band's' is the wordplay.
I cannot really see how this works, but
'about' could be 'a' (abbreviation in Chambers) and 'a' is located in the answer.
'energy' could be 'oomph' (I've seen this before) and 'oomph' is present in the remaining letters.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for oompah that I've seen before include "Deep-toned noise of brass instruments" , "Noise of brass (colloq.)" , "Bierkeller sort of band" , "A Sound of Music" , "Sound of deep brass instrument (colloq.)" .)