Orchestra part (5)
(Other definitions for cello that I've seen before include "Viola's bigger brother?" , "Large stringed instrument" , "Bass stringed instrument" , "has strings attached" , "Instrument in the violin family" .)
'orchestra part' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oboe that I've seen before include "Cor anglais in its family" , "Walk with exaggerated movements" , "Woodwind instrument of treble pitch" , "Instrument used in 1d" , "Double-reed wind instrument" .)