One caring perhaps but not knowing (9)
I believe the answer is:
ignorance
'not knowing' is the definition.
(I've seen this before)
'one caring perhaps' is the wordplay.
'perhaps' indicates an anagram.
'one'+'caring'='onecaring'
'onecaring' anagrammed gives 'IGNORANCE'.
'but' acts as a link.
(Other definitions for ignorance that I've seen before include "Ken lacking" , "lack of awareness" , "Not knowing" , "being uninformed" , "Lack of knowledge" .)