Strand most of non-professional troops in sound (8)
I believe the answer is:
filament
'strand' is the definition.
('filament' can be a synonym of 'strand')
'most of non-professional troops in sound' is the wordplay.
'most of' means to remove the last letter.
'non-professional' becomes 'lay' (I've seen this before).
'troops' becomes 'men' (I've seen this in other clues**).
'in' is an insertion indicator.
'sound' becomes 'fit' ('fit' is associated in meaning with 'sound').
'lay' with its final letter taken off is 'la'.
'la'+'men'='lamen'
'lamen' put inside 'fit' is 'FILAMENT'.
(Other definitions for filament that I've seen before include "Wire in incandescent bulb" , "Strand" , "Part of light" , "Thread-like object" , "Wire in light bulb" .)