Material of which there are fifty-nine varieties (5)
I believe the answer is:
linen
'material of which there' is the definition.
'linen' can be an answer for 'material' (linen is a kind of material). I'm unsure of the rest of the definition.
'fifty-nine varieties' is the wordplay.
'fifty' becomes 'l' (Roman numeral).
'varieties' indicates anagramming the letters (I've seen 'variety' mean this).
'nine' with letters rearranged gives 'inen'.
'l'+'inen'='LINEN'
'are' is the link.
Can you help me to learn more?
(Other definitions for linen that I've seen before include "Flax product" , "Flaxen cloth" , "Flax textile" , "Cloth woven flax fibres" , "Such paper" .)