Marsh plants (5)
'marsh plants' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for reeds that I've seen before include "Long grasses" , "Thatching stalks" , "Tall stiff marsh grasses" , "Stops" , "Thin pieces of cane in musical instruments" .)
(Another definition for segos that I've seen is " US plants".)
'marsh plants' is the definition.
(cattail is a kind of marsh plant)
This is the entire clue.