Space traveller cut as moon explodes (9)
I believe the answer is:
cosmonaut
'space traveller' is the definition.
(I know that space traveller can be written as cosmonaut)
'cut as moon explodes' is the wordplay.
'explodes' is an anagram indicator.
'cut'+'as'+'moon'='cutasmoon'
'cutasmoon' anagrammed gives 'COSMONAUT'.
(Other definitions for cosmonaut that I've seen before include "Spaceman" , "Yuri Gagarin, for example" , "Long distance traveller" , "Russian space traveller" .)