Distant object is old copper (8)
I believe the answer is:
farthing
'old copper' is the definition.
(former UK coin)
'distant object' is the wordplay.
'distant' becomes 'far' ('far' can be similar in meaning to 'distant').
'object' becomes 'thing' (thing is a kind of object).
'far'+'thing'='FARTHING'
'is' acts as a link.
(Other definitions for farthing that I've seen before include "Former British coin" , "One quarter of an old penny: measure of land in old England" , "Old quarter of a penny is a remote object" , "Old British coin" , "of negligible value" .)