Worsen, inflame (9)
I believe the answer is:
aggravate
I believe this is a double definition.
'worsen' is the first definition.
(synonyms)
'inflame' is the second definition.
(thesaurus)
(Other definitions for aggravate that I've seen before include "Annoy; make worse" , "Make (a problem) worse" , "Make more serious" , "Make a bad situation worse" , "Pester" .)