A clock that sounds the hour; a wild idea (7)
I believe the answer is:
chimera
'wild idea' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for chimera that I've seen before include "Fantastic creation of the mind, like Greek mythical monster" , "Illusory goal; monster" , "Imaginary monster" , "fabulous beast" , "Illusory achievement; mythical beast" .)