Small step taken by male astronaut (8)
I believe the answer is:
spaceman
'astronaut' is the definition.
(I know that astronaut can be written as spaceman)
'small step taken by male' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'step' becomes 'pace' (synonyms).
'taken by' says to put letters next to each other.
'male' becomes 'man' (man is a kind of male).
's'+'pace'+'man'='SPACEMAN'
(Other definitions for spaceman that I've seen before include "one requiring a supply of oxygen?" , "Astronaut" , "High flier" , "NASA PC, me! (anag)" , "Distant traveller" .)