Lip in severe pain, bringing medicinal herb (8)
I believe the answer is:
agrimony
'medicinal herb' is the definition.
'lip in severe pain' is the wordplay.
'lip' becomes 'rim' ('rim' can be a synonym of 'lip').
'in' indicates putting letters inside.
'severe pain' becomes 'agony' (I've seen this before).
'rim' put inside 'agony' is 'AGRIMONY'.
'bringing' acts as a link.
(Other definitions for agrimony that I've seen before include "Growth" , "Plant with yellow flower-spikes" .)