Badger, hound, and nag (6)
I believe the answer is:
harass
I believe this clue is a triple definition!
'badger' is the first definition.
('harass' can be a synonym of 'badger')
'hound' is the second definition.
(I've seen this before)
'and' is a link.
'nag' is the third definition.
(I've seen this before)
(Other definitions for harass that I've seen before include "Vex - pester" , "bait" , "Vex - persecute" , "Annoy persistently, persecute" , "Disturb < badger" .)