Afflicts (4)
I believe the answer is:
ails
'afflicts' is the definition.
('ail' can be a synonym of 'afflict')
This is the entire clue.
(Other definitions for ails that I've seen before include "Is unwell - sail away" , "Feels unwell" , "Is sick" , "Troubles; afflicts" , "Is ill or uneasy - sail away" .)