Taste sour, outwardly? (6)
I believe the answer is:
savour
This clue might be a double definition.
'taste' is the first definition.
(synonyms)
'sour outwardly?' is the second definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
Can you help me to learn more?
(Other definitions for savour that I've seen before include "Characteristic taste" , "Enjoy taste of (food)" , "Relish, enjoy" , "Taste, relish" , "Enjoy the flavour" .)