Mailer's conversion to practical appreciation (7)
I believe the answer is:
realism
'practical appreciation' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'mailer's conversion' is the wordplay.
'conversion' indicates an anagram.
'mailers' with letters rearranged gives 'REALISM'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for realism that I've seen before include "Practical approach" , "Reliance on facts" , "Practicality of mailers" , "Awareness of the facts of life" , "Pragmatic view" .)