Lifeline site (4)
I believe the answer is:
palm
'lifeline site' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for palm that I've seen before include "Sign of victory" , "Evergreen tree and part of the hand" , "that's inspected by a fortune-teller" , "Tree symbolising victory" , "Tropical tree; conceal" .)