Piano maker half polishes piano, preferring one side (12)
I believe the answer is:
partisanship
'side' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'piano maker half polishes piano preferring one' is the wordplay.
I cannot quite understand how this works, but
'piano' could be 'p' (musical abbreviation) and 'p' is located in the answer.
'one' could be 'an' (an apple is one apple) and 'an' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for partisanship that I've seen before include "Taking sides" , "Factionalism" , "One-sided support" .)