Escape quickly authorised? (5)
I believe the answer is:
legit
I believe this is a double definition.
'escape quickly' is the first definition.
(to leg it is to run away)
'authorised?' is the second definition.
(legitimate)
(Other definitions for legit that I've seen before include "ok!" , "Not illegal" , "Conforming to the law" , "allowed by law, shortly!" , "Reliable" .)