Churning up bonfire for an analgesic (9)
I believe the answer is:
ibuprofen
'for an analgesic' is the definition.
(ibuprofen is a kind of analgesic)
'churning up bonfire' is the wordplay.
'churning' indicates anagramming the letters.
'up'+'bonfire'='upbonfire'
'upbonfire' with letters rearranged gives 'IBUPROFEN'.
(Other definitions for ibuprofen that I've seen before include "Painkiller" , "Anti-inflammatory medicine" , "anaesthetic" , "Drug" .)