Therefore depart after a little hesitation (4)
I believe the answer is:
ergo
'therefore' is the definition.
(I've seen this before)
'depart after a little hesitation' is the wordplay.
'depart' becomes 'go' (synonyms).
'after' is a charade indicator (letters next to each other).
'a little hesitation' becomes 'er' (expression of hesitation).
'go' put after 'er' is 'ERGO'.
(Other definitions for ergo that I've seen before include "'Therefore, to the old Romans (4)'" , "Thus" , "as a consequence" , "for this reason" , "Consequently" .)