NASA spacewalk (3)
I believe the answer is:
eva
'nasa spacewalk' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for eva that I've seen before include "Dame - - Turner, 15" , "Female" , "Girl's name; extravehicular activity (abbreviation)" , "Maria -- Duarte De Peron" , "-- Cassidy, singer, 1963-96" .)