Sing, making racket, causing first pair to leave in anger - it's a remarkable thing (9)
I believe the answer is:
humdinger
'thing' is the definition.
(I have seen 'excellent thing' mean 'humdinger' so perhaps 'thing' could also mean 'humdinger')
'sing making racket' is the wordplay.
'sing' becomes 'hum' (humming is a kind of singing).
'making racket' becomes 'dinger' (I can't justify this - if you can you should give a lot more credence to this answer).
'hum'+'dinger'='HUMDINGER'
'causing first pair to leave in anger it's a remarkable' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for humdinger that I've seen before include "something else" , "Excellent example" , "cracker" , "excellent specimen" , "Something very large or excellent" .)