Church plays a role in disease (7)
I believe the answer is:
cholera
'disease' is the definition.
(cholera is a kind of disease)
'church plays a role' is the wordplay.
'church' becomes 'ch' (common abbreviation**).
'plays' indicates an anagram.
'a'+'role'='arole'
'arole' is an anagram of 'olera'.
'ch'+'olera'='CHOLERA'
'in' acts as a link.
(Other definitions for cholera that I've seen before include "Deadly, infectious disease" , "Acute intestinal infection from contaminated water or food" , "Disease caught from contaminated water" , "Infectious and often fatal intestinal disease (7" , "A severe intestinal disease, severe Asiatic kind" .)