Ingredient in some soap (4)
I believe the answer is:
aloe
'ingredient in some soap' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aloe that I've seen before include "Bitter fruit" , "Succulent plant (may be bitter!)" , "O, ale with bitter plant" , "Fleshy-leaved plant" , "has a bitter taste" .)