Horticulturally, various things are tied up with it (6)
I believe the answer is:
raffia
'it' is the definition.
The definition suggests a singular noun which matches the answer.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for raffia that I've seen before include "Leaves used in mats and baskets" , "Fibre from palm tree, used to make mats" , "Fibre for making baskets, etc" , "a Madagascan basket-maker" , "Palm leaves used in weaving" .)