Digestive chemical (6)
I believe the answer is:
enzyme
'digestive chemical' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for enzyme that I've seen before include "Substance created in living cells acting as a catalyst" , "One causing a reaction" , "Catalytic protein substance" , "Cell-produced protein" , "Catalyst made of protein" .)