Wide outbreak of pied mice disrupted (8)
I believe the answer is:
epidemic
'wide outbreak' is the definition.
'pied mice disrupted' is the wordplay.
'disrupted' is an anagram indicator.
'pied'+'mice'='piedmice'
'piedmice' anagrammed gives 'EPIDEMIC'.
'of' is the link.
(Other definitions for epidemic that I've seen before include "health emergency" , "Unfortunately widespread" , "Disease affecting many people simultaneously" , "Outbreak of disease which spreads rapidly" , "Plague" .)