Kind heart turning ignorant (2,3,4)
I believe the answer is:
in the dark
'ignorant' is the definition.
(in the dark means being ignorant about something)
'kind heart turning' is the wordplay.
'turning' indicates anagramming the letters.
'kind'+'heart'='kindheart'
'kindheart' anagrammed gives 'IN THE DARK'.
(Other definitions for in the dark that I've seen before include "Ill-informed" , "Not knowing" , "overnight" , "Told nothing" , "Ignorant, unaware" .)