As a result, there's an egression (7)
I believe the answer is:
outcome
'there's an egression' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for outcome that I've seen before include "Result or consequence" , "Eventuality" , "Denouement" , "Consequence, upshot" , "'Result, upshot (7)'" .)