One old-fashioned object of veneration (4)
I believe the answer is:
idol
'object of veneration' is the definition.
(I've seen this in another clue)
'one old-fashioned' is the wordplay.
'one' becomes 'i' (Roman numeral).
'fashioned' indicates an anagram.
'old' is an anagram of 'dol'.
'i'+'dol'='IDOL'
(Other definitions for idol that I've seen before include "loved one" , "Graven image (sometimes false?)" , "Object of reverence" , "Object of excessive adoration" , "Object of excessive love or devotion" .)