Pesters some nocturnal animals (7)
I believe the answer is:
badgers
This clue is a double definition.
'pesters' is the first definition.
('badger' can be a synonym of 'pester')
'some nocturnal animals' is the second definition.
(Other definitions for badgers that I've seen before include "Bullies" , "Burrowing mammals with strong claws" , "Pesters like burrowing animals" , "Pesters; black and white nocturnal animals" .)