Asian king's quiet sound of realisation (4)
I believe the answer is:
shah
'asian king's' is the definition.
'shah' can be an answer for 'king's' (I have seen 'King of Persia' mean 'shah' so perhaps 'king' could also mean 'shah'). I'm not certain of the 'asian' bit.
'quiet sound of realisation' is the wordplay.
'quiet' becomes 'sh' ('sh' is used to tell someone to be quiet).
'sound of realisation' becomes 'ah' (I can't explain this - if you can you should believe this answer much more).
'sh'+'ah'='SHAH'
Can you help me to learn more?
(Other definitions for shah that I've seen before include "Persian emperor" , "Sovereign ousted in 1979" , "Emperor of Iran" , "Former ruler of Persia" , "King of Persia" .)