Leave with pater, travelling the day before (6)
I believe the answer is:
depart
'leave' is the definition.
(I know that depart is a more specific form of the action leave)
'pater travelling the day before' is the wordplay.
'travelling' indicates an anagram.
'the day' becomes 'd' (abbreviation for day).
'before' is a charade indicator (letters next to each other).
'pater' anagrammed gives 'epart'.
'epart' put after 'd' is 'DEPART'.
'with' is the link.
(Other definitions for depart that I've seen before include "make tracks" , "Clearly expressive" , "Prated (anag.)" , "Make an exit" , "Stray" .)