Transcend extravagant endless pain (8)
I believe the answer is:
'transcend' is the definition.
(to transcend is to reach or go further than)
'extravagant endless pain' is the wordplay.
'extravagant' becomes 'outre' (outre can mean extravagant or eccentric).
'endless' means to remove the last letter.
'pain' becomes 'ache' (ache is a kind of pain).
'ache' with its last letter taken away is 'ach'.
(Other definitions for outreach that I've seen before include "Work in the community", "Evangelistic activity", "Stretch forth", "Organisation's influence in the community", "spreading the message further afield?".)