It's human right to take time (6)
I believe the answer is:
mortal
'it's human' is the definition.
('mortal' can be a synonym of 'human')
'right to take time' is the wordplay.
I cannot really understand how this works, but
'right' could be 'rt' and 'rt' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for mortal that I've seen before include "Fatal" , "Certain to die" , "Human being, subject to death" , "liable to die" , "Liable to cause death" .)