Demanding, strict (8)
I believe the answer is:
exacting
I believe this is a double definition.
'demanding' is the first definition.
(exacting is a kind of demanding)
'strict' is the second definition.
(I know that strict can be written as exacting)
(Other definitions for exacting that I've seen before include "Making great demands like difficult task" , "Demanding in effort - or money" , "Demanding much" , "Tough" , "Strict, demanding" .)