Find stern tests all exposed curiosity (8)
I believe the answer is:
interest
'curiosity' is the definition.
(interest is a kind of curiosity)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for interest that I've seen before include "Gain - attention" , "Gain - curiosity" , "Condition of curiosity about amount paid for use of money" , "earnings" , "Hobby" .)