Ether, quaint number (5)
I believe the answer is:
three
'number' is the definition.
(three is a number)
'ether quaint' is the wordplay.
'ether' can be anagrammed to 'THREE'.
Though, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for three that I've seen before include "Trinity, triad" , "Cardinal number" , "trilogy" , "Sixth root of seven hundred and twenty nine" , "Bears or blind mice" .)