Provision to leave space, as clue confused editor initially (6,6)
I believe the answer is:
escape clause
'provision to leave' is the definition.
(provision allowing one to leave)
'space as clue confused editor initially' is the wordplay.
'confused' indicates anagramming the letters.
'initially' says to take the initial letters.
The initial letter of 'editor' is 'e'.
'space'+'as'+'clue'='spaceasclue'
'spaceasclue' anagrammed gives 'escapeclaus'.
'escapeclaus'+'e'='ESCAPE CLAUSE'
(Other definitions for escape clause that I've seen before include "Way out of a contract" , "Release mechanism" , "legal get-out" .)