One form of trust (4)
I believe the answer is:
unit
This might be a double definition.
'one' is the first definition.
(synonyms)
'form of trust' is the second 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?
Can you help me to learn more?
(Other definitions for unit that I've seen before include "Module" , "detachment maybe" , "army group" , "Subdivision of a military group" , "Single item; one" .)