Radio set especially designed for a space traveller (8)
I believe the answer is:
asteroid
'a space traveller' is the definition.
(I've seen this before)
'radio set especially designed' is the wordplay.
'especially designed' indicates an anagram (letters re-designed in a particular way).
'radio'+'set'='radioset'
'radioset' anagrammed gives 'ASTEROID'.
'for' acts as a link.
(Other definitions for asteroid that I've seen before include "Small planet orbiting the Sun" , "Minor planet" , "Any of the small planets revolving around the sun" , "could be dangerous for astronauts" , "Bits of rock that move around the heavens" .)