Salve ingredient (4)
I believe the answer is:
aloe
'salve ingredient' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aloe that I've seen before include "shrub" , "O, ale with bitter plant" , "Bitter drug from a leaf juice" , "Plant source of purgative drug" , "Genus of bitter herbs" .)