Underwear made from artificial fibres? (6)

I believe the answer is:
briefs
'underwear' is the definition.
(I know that briefs is a type of underpants)
'from artificial fibres?' is the wordplay.
'fibres' anagrams to 'BRIEFS'.
However, I am not clear how the anagram is indicated.
'made' is the link.
Can you help me to learn more?
(Other definitions for briefs that I've seen before include "Underwear and lawyer's documents" , "Digests" , "by which privates will be constrained" , "Gives information and instructions (to)" , "Underpants for a lawyer" .)