Holiday abroad precedes epidemic (8)
I believe the answer is:
outbreak
'epidemic' is the definition.
(I've seen this before)
'holiday abroad precedes' is the wordplay.
'holiday' becomes 'break' (I've seen this before).
'abroad' becomes 'out' (I've seen this before).
'precedes' is a charade indicator (letters next to each other).
'break' after 'out' is 'OUTBREAK'.
(Other definitions for outbreak that I've seen before include "Violent occurrence" , "Sudden spontaneous occurrence" , "Eruption of e.g. disease" , "Sudden occurrence (of war, disease, etc.)" , "rash" .)