Be ecstatic, about to escape former sect (5)
I believe the answer is:
exult
'be ecstatic' is the definition.
(to exult in something is to be ecstatic about it)
'former sect' is the wordplay.
'former' becomes 'ex'.
'sect' becomes 'ult' (I can't explain this - if you can you should believe this answer much more).
'ex'+'ult'='EXULT'
'about to escape' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
(Other definitions for exult that I've seen before include "Feel triumphant elation" , "Be jubilant" , "Be intensely joyful" , "Crow in triumph" , "Show triumphant joy" .)