Instrument that plays my number the wrong way (6)
I believe the answer is:
cornet
'instrument that plays' is the definition.
'cornet' can be an answer for 'instrument' (cornet is a kind of instrument). I am not sure about the rest of the definition.
'my number the wrong way' is the wordplay.
'my' becomes 'cor' (both are expressions of surprise).
'number' becomes 'ten' (ten is a kind of whole number).
'the wrong way' says the letters should be written backwards.
'ten' written backwards gives 'net'.
'cor'+'net'='CORNET'
Can you help me to learn more?
(Other definitions for cornet that I've seen before include "Wind instrument" , "Musical instrument like small trumpet" , "play this?" , "A short trumpet or ice-cream holder" , "Kind of trumpet, or ice cream holder" .)