Without pity (11)
I believe the answer is:
remorseless
'without pity' is the definition.
('pity' can be 'remorse' (I've seen this before) so maybe 'without pity' can be ''remorseless')
This is the entire clue.
(Other definitions for remorseless that I've seen before include "Relentless" , "Implacable" , "Cruel; without respite" , "Unmerciful" , "Not letting up," .)