Best policy for decreasing the prison population (7)
I believe the answer is:
honesty
'best policy' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for honesty that I've seen before include "Fairness" , "Straightforwardness" , "A virtue" , "Plant; truthfulness" , "Uprightness" .)