Learning it? A dunce unfortunately retains nothing (9)
I believe the answer is:
education
'learning' is the definition.
(I've seen this before)
'it? a dunce unfortunately retains nothing' is the wordplay.
'unfortunately' indicates an anagram.
'retains' is an insertion indicator.
'nothing' becomes 'o' (looks like zero - 0).
'it'+'a'+'dunce'='itadunce'
'itadunce' anagrammed gives 'educatin'.
'educatin' enclosing 'o' is 'EDUCATION'.
(Other definitions for education that I've seen before include "Series of activities that impart knowledge or skill" , "Schooling, instruction" , "studies" , "Blair's triple mantra" , "training" .)