Something to cut out (6)
I believe the answer is:
coupon
'cut out' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for coupon that I've seen before include "Voucher or ticket" , "betting slip" , "means to buy goods" , "Entry form" , "Token" .)