Centaurs conjured up in an ancient civilisation (8)
I believe the answer is:
etruscan
'an ancient civilisation' is the definition.
(the Etruscans were an ancient people)
'centaurs conjured up' is the wordplay.
'conjured up' is an anagram indicator (I've seen 'conjuring up' mean this).
'centaurs' anagrammed gives 'ETRUSCAN'.
'in' acts as a link.
(Other definitions for etruscan that I've seen before include "Pre-Roman Italian" , "Early Roman" , "of an ancient civilization" , "from part of old Italy" , "Centaurs (anag) -- native of an ancient state of central Italy" .)