That is Victor wearing decoration from long ago (8)
I believe the answer is:
medieval
'from long ago' is the definition.
(from the Middle Ages)
'that is victor wearing decoration' is the wordplay.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'victor' becomes 'V' (phonetic alphabet: alpha, bravo, charlie etc.).
'wearing' is an insertion indicator.
'decoration' becomes 'medal' (synonyms).
'ie'+'v'='iev'
'iev' inserted within 'medal' is 'MEDIEVAL'.
(Other definitions for medieval that I've seen before include "Belonging to the Middle Ages" , "Of an earlier period" , "Relating to the Middle Ages" , "Am veiled in style of the middle ages" , "Of the middle ages, or really old-fashioned" .)