Cool part in prevalent epidemic (5)
I believe the answer is:
tepid
'cool' is the definition.
(thesaurus)
'part in prevalent epidemic' is the wordplay.
'part in' indicates a hidden word.
'TEPID' is hidden within 'prevalent epidemic'.
(Other definitions for tepid that I've seen before include "Not very enthusiastic" , "Showing little interest or enthusiasm" , "Unenthusiastic - cool" , "Of liquid, luke-warm" , "Warmish" .)