Sharp marinade (5)
I believe the answer is:
steep
I believe this is a double definition.
'sharp' is the first definition.
(similar in meaning)
'marinade' is the second definition.
(I know that marinade is a more specific form of the action steep)
(Other definitions for steep that I've seen before include "Precipitous - exorbitant" , "Lofty" , "Almost perpendicular" , "Sheer, precipitous" , "Having a sharp incline" .)