Annoys by reassessing risk (4)
I believe the answer is:
irks
'annoys' is the definition.
(I've seen this before)
'reassessing risk' is the wordplay.
'reassessing' indicates an anagram.
'risk' is an anagram of 'IRKS'.
'by' acts as a link.
(Other definitions for irks that I've seen before include "Annoys, vexes" , "Galls" , "Annoys, irritates" , "'Irritate, annoy (4)'" .)