Little dog who’ll be quiet when ordered? (3)
I believe the answer is:
pom
'little dog' is the definition.
(I've seen this before)
'quiet when ordered?' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano').
'when ordered?' becomes 'om' (I can't explain this - if you can you should give a lot more credence to this answer).
'p'+'om'='POM'
'who'll be' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for pom that I've seen before include "Brit abroad" , "Englishman in Australia" , "Limey in Oz" , "Pomeranian dog" , "Australian slang for British migrant" .)