Space-man yawned (5)
I believe the answer is:
gaped
'yawned' is the definition.
('gape' can be a synonym of 'yawn')
'space-man' is the wordplay.
'space' becomes 'gap' (gap is a kind of space**).
'man' becomes 'ed'.
'gap'+'ed'='GAPED'
(Other definitions for gaped that I've seen before include "Looked stunned" , "Stared open-mouthed - yawned" , "shown astonishment" , "Was yawning" , "Opened mouth wide" .)