Swamp tree (8)
I believe the answer is:
mangrove
'swamp tree' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for mangrove that I've seen before include "Swamp tree" , "that grows in swamps" , "Tree growing on tropical coasts and in muddy swamps" , "one that's swamped?" , "Tree of coastal swamps" .)