Knowledge obtained from cautioned suspect (9)
I believe the answer is:
education
'knowledge' is the definition.
(I know that education is a type of learning)
'cautioned suspect' is the wordplay.
'suspect' indicates an anagram (a suspicious or unusual spelling).
'cautioned' is an anagram of 'EDUCATION'.
'obtained from' is the link.
(Other definitions for education that I've seen before include "training" , "Work of master" , "Academy's aim" , "New Labour mantra, when repeated" , "Teaching - knowledge" .)