Matted weeds used as a vegetable (5)
I believe the answer is:
swede
'vegetable' is the definition.
(swede is a kind of vegetable)
'matted weeds used as a' is the wordplay.
'weeds' can be anagrammed to 'SWEDE'.
Though, I'm unsure how this is indicated.
Can you help me to learn more?
(Other definitions for swede that I've seen before include "North European" , "Citizen of kingdom" , "A turnip, or a Scandinavian" , "Northern European" , "Root vegetable - European" .)