Quality of theatre company leading us in acts, I fancy (9)
I believe the answer is:
acoustics
'quality of theatre' is the definition.
The definition and answer 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?
'company leading us in acts i fancy' is the wordplay.
'company' becomes 'co' (abbreviation).
'leading' says to put letters next to each other (some letters go in front of others).
'in' means one lot of letters goes inside another.
'fancy' indicates an anagram.
'co'+'us'='cous'
'acts'+'i'='actsi'
'actsi' anagrammed gives 'atics'.
'cous' inserted inside 'atics' is 'ACOUSTICS'.
Can you help me to learn more?
(Other definitions for acoustics that I've seen before include "Science of sound" , "So caustic about properties of sound" , "The study of the properties of sound" , "CIA scouts seeking properties of sound" .)