Hound (6)
(Other definitions for nag that I've seen before include "Complain, worry" , "Scold persistently, annoy" , "Scold like an old horse" , "Jade" , "(Of pain) ache dully; horse (colloq.)" .)
'hound' is the definition.
(I know that hound can be written as dog)
This is the entire clue.
(Other definitions for dog that I've seen before include "'You cannot teach an old ... new tricks'" , "Cur" , "Domesticated canine" , "Follow - canine" , "Follow closely; animal" .)
'hound' is the definition.
(basset hound is an example)
This is the entire clue.
(Other definitions for basset that I've seen before include "Hound with short legs and long ears" , "Beasts (anag.)" , "Short-legged hound that hunts hares" , "Smooth-haired, long-eared hound" , "Hound (named Fred?)" .)
(Other definitions for chivvy that I've seen before include "Pester - chase" , "Annoy continually" , "Badger" , "Encourage" , "Keep on asking" .)