Gongs comprising orchestra's earliest instruments (5)
I believe the answer is:
oboes
'earliest instruments' is the definition.
'oboes' can be an answer for 'instruments' (I've seen this in another clue). I am not certain of the 'earliest' bit.
'gongs comprising orchestra's' is the wordplay.
'gongs' becomes 'OBEs' (Order of the British Empire awards).
'comprising' indicates putting letters inside.
'orchestra's' becomes 'o' (this could be a standard abbreviation which I don't know about).
'obes' enclosing 'o' is 'OBOES'.
Can you help me to learn more?
(Other definitions for oboes that I've seen before include "They're instrumental" , "Parts of orchestra" , "Wind instruments" , "noted producers" , "members of orchestra" .)