Order parts for ordinary instrument (4)
I believe the answer is:
oboe
'instrument' is the definition.
(type of musical instrument)
'order parts for ordinary' is the wordplay.
'parts' says to take the initial letters (I've seen 'part' mean this).
'for' is a charade indicator (letters next to each other).
'ordinary' becomes 'boe' (I can't justify this - if you can you should give a lot more credence to this answer).
The initial letter of 'order' is 'o'.
'o'+'boe'='OBOE'
Can you help me to learn more?
(Other definitions for oboe that I've seen before include "Instrument used in 1d" , "Slender double-reed instrument" , "Producer of notes" , "bit of wind" , "Player" .)