An organ for music (3)
I believe the answer is:
ear
This could be a double definition.
'an organ' is the first definition.
(the ear is an organ)
'music' is the second definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'for' acts as a link.
Can you help me to learn more?
(Other definitions for ear that I've seen before include "A corny bit" , "Fruiting head of corn" , "Speculator ignoring British" , "Aural organ" , "Organ inside heart" .)