Eccentric space-traveller (6)
I believe the answer is:
meteor
'eccentric' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'space-traveller' is the wordplay.
I cannot quite see how this works, but
'space traveller' could be 'et' (I've seen this in other clues) and 'et' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for meteor that I've seen before include "rock falling to earth" , "Remote (anag)" , "Small extraterrestrial body" , "Falling star" , "A space-traveller" .)