Wise fool that is not heartless (7)
I believe the answer is:
sapient
'wise' is the definition.
(I've seen this before)
'fool that is not heartless' is the wordplay.
'fool' becomes 'sap' ('sap' can be a synonym of 'fool'**).
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'heartless' says to hollow out the word (remove centre letters).
'not' with its middle taken out is 'nt'.
'sap'+'ie'+'nt'='SAPIENT'
(Other definitions for sapient that I've seen before include "very keen" , "Discerning" , "of great wisdom" , "Canny" , "Acutely insightful and wise" .)