Rooster, an aberrant reverberating entity (9)
I believe the answer is:
resonator
'reverberating entity' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'rooster an aberrant' is the wordplay.
'aberrant' indicates anagramming the letters.
'rooster'+'an'='roosteran'
'roosteran' is an anagram of 'RESONATOR'.
Can you help me to learn more?
(Other definitions for resonator that I've seen before include "Tuned circuitry" , "Device amplifying sound" , "Sounding vessel" , "Device for enhancing oscillations" .)