Cart fate about - that's not natural (8)
I believe the answer is:
artefact
'not natural' is the definition.
(I've seen this before)
'cart fate about' is the wordplay.
'about' is an anagram indicator.
'cart'+'fate'='cartfate'
'cartfate' anagrammed gives 'ARTEFACT'.
'that's' acts as a link.
(Other definitions for artefact that I've seen before include "Thing made by human workmanship" , "Man-made object, of archaeological interest, perhaps" , "Man-made object, of archaeological interest say" , "not natural" , "Something man made" .)