Tolerant principle in assize: a lifer released (7,5)
I believe the answer is:
laissez faire
'tolerant principle' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'assize a lifer released' is the wordplay.
'released' is an anagram indicator (letters released from their original order).
'assize'+'a'+'lifer'='assizealifer'
'assizealifer' is an anagram of 'LAISSEZ-FAIRE'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for laissez faire that I've seen before include "Principle of non-interference" , "Non-interventionist" , "hands-off policy" , "Doctrine that governments should not interfere in commercial matters" , "without trying to direct" .)