Voice peddle on top of orchestral instrument (5)
I believe the answer is:
cello
'instrument' is the definition.
(cello is a kind of instrument)
'voice peddle on top of orchestral' is the wordplay.
'voice' indicates a 'sounds like' (homophone) clue (I've seen 'voiced' mean this).
'peddle' becomes 'sell' (I've seen this in another clue).
'on top of' says to take the initial letters.
The initial letter of 'orchestral' is 'o'.
'sell' sounds like 'cell'.
'cell'+'o'='CELLO'
(Other definitions for cello that I've seen before include "Bass stringed instrument" , "String quartet instrument" , "Musical instrument like large violin held between legs" , "has strings attached" , "Bowed musical instrument" .)