Last couple escaping death in Great Plague (8)
I believe the answer is:
epidemic
'plague' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for epidemic that I've seen before include "Dim piece (anag)" , "Widespread occurrence of a disease" , "Unfortunately widespread" , "Rash" , "medical emergency" .)