Leave with hesitation, therefore (4)
I believe the answer is:
ergo
'therefore' is the definition.
(thesaurus)
'leave with hesitation' is the wordplay.
'leave' becomes 'go'.
'with' says to put letters next to each other.
'hesitation' becomes 'er'.
'go' put after 'er' is 'ERGO'.
(Other definitions for ergo that I've seen before include "It follows" , "'Cogito, ---- sum'" , "Thus" , "Hence" , "for this reason" .)