One heading for quarry before fourth schedule's drawn up? (8)
I believe the answer is:
predator
'one heading for quarry' is the definition.
(quarry can mean prey)
'before fourth schedule's drawn up?' is the wordplay.
I cannot really see how this works, but
'before' could be 'pre' and 'pre' is found in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for predator that I've seen before include "One preying on others" , "One seeking victim" , "Parroted like one who exploits others" , "Exploitative person" , "Beast of prey" .)