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