Room on isle for astronaut (8)
I believe the answer is:
spaceman
'for astronaut' is the definition.
(synonyms)
'room on isle' is the wordplay.
'room' becomes 'space' (I've seen this in another clue).
'on' says to put letters next to each other.
'isle' becomes 'man' (the Isle of Man is an example).
'space'+'man'='SPACEMAN'
(Other definitions for spaceman that I've seen before include "Out-of-this-world chap?" , "Distant traveller" , "Astronaut" , "Armstrong, perhaps?" , "Armstrong, say" .)