One garment, of which five make a set (4)
I believe the answer is:
vest
'one garment of which' is the definition.
'vest' can be an answer for 'one garment' (vest is a type of garment or item of clothing). I am unsure of the remainder of the definition.
'five make a set' is the wordplay.
'five' becomes 'v' (Roman numeral).
'make' indicates anagramming the letters.
'set' is an anagram of 'est'.
'v'+'est'='VEST'
Can you help me to learn more?
(Other definitions for vest that I've seen before include "American version of waistcoat" , "Undergarment covering trunk of body" , "Upper undergarment, singlet" , "Sleeveless garment" , "Thesaurus compiler" .)