Badger is safe, protecting entrance to sett (6)
I believe the answer is:
pester
'badger' is the definition.
(I've seen this before)
'safe protecting entrance to sett' is the wordplay.
'safe' becomes 'peter' (I've seen this before).
'protecting' is an insertion indicator.
'entrance to' says to take the initial letters.
The first letter of 'sett' is 's'.
'peter' placed around 's' is 'PESTER'.
'is' is the link.
(Other definitions for pester that I've seen before include "Harass" , "Channel island" , "Annoy with persistent requests" , "Nag, badger" , "Importune" .)