Show mercy (6)
I believe the answer is:
relent
'show mercy' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for relent that I've seen before include "Acquiesce" , "'Give in, soften (6)'" , "Soften, grow less severe" , "Become less severe, soften" , "Relax severity or opposition" .)