Hardhearted, pitiless (6)
I believe the answer is:
unkind
I believe this is a double definition.
'hardhearted' is the first definition.
(I've seen this before)
'pitiless' is the second definition.
(I know that pitiless can be written as unkind)
(Other definitions for unkind that I've seen before include "Thoughtless -- inhumane" , "Uncaring, not generous" , "Mean, pitiless" , "Cold-hearted" , "Not gentle or considerate" .)