Remain prepared for plague (5)
I believe the answer is:
beset
'plague' is the definition.
('beset' can be a synonym of 'plague')
'remain prepared' is the wordplay.
'remain' becomes 'be' (I've seen this in other clues).
'prepared' becomes 'set' (I've seen this before).
'be'+'set'='BESET'
'for' is the link.
(Other definitions for beset that I've seen before include "Harry" , "Hem in, afflict" , "surrounded by hostile forces" , "Trouble or harass persistently" , "Assail (with problems?)" .)