Anger over a contagious disease (7)
I believe the answer is:
cholera
'contagious disease' is the definition.
(I've seen this before)
'anger over a' is the wordplay.
'anger' becomes 'choler' ('choler' can be a synonym of 'anger'**).
'over' means one lot of letters go next to another.
'choler'+'a'='CHOLERA'
(Other definitions for cholera that I've seen before include "Intestinal infection caused by contaminated water or food" , "could kill you" , "bacterial disease" , "Infectious and often fatal intestinal disease (7" , "Disease caught from contaminated water" .)