Strict, unforgiving (5)
I believe the answer is:
harsh
I believe this clue is a double definition.
'strict' is the first definition.
(I've seen this in another clue)
'unforgiving' is the second definition.
(I've seen this in another clue)
(Other definitions for harsh that I've seen before include "Punitive" , "Severe - unkind" , "Raucous - austere - bitter" , "Not relenting" , "Rough and disagreeable, maybe of voice" .)