Badger's regular route below summit (8)
I believe the answer is:
browbeat
'badger's' is the definition.
(thesaurus)
'regular route below summit' is the wordplay.
'regular route' becomes 'beat' (eg a police officer's beat).
'below' means one lot of letters go next to another.
'summit' becomes 'brow' (brow is a kind of summit).
'beat' after 'brow' is 'BROWBEAT'.
(Other definitions for browbeat that I've seen before include "Bully verbally" , "Intimidate, bulldoze" , "Hector" , "Bully or intimidate - using forehead?" , "cow" .)