Pester, bother (6)
I believe the answer is:
harass
I believe this is a double definition.
'pester' is the first definition.
(synonyms)
'bother' is the second definition.
(I know that harass is a type of bother)
(Other definitions for harass that I've seen before include "Vex - persecute" , "Nag" , "Intimidate, torment" , "Continually torment" , "Constantly intimidate" .)