Expert performed outside space walk (9)
I believe the answer is:
promenade
'walk' is the definition.
(I know that promenade is a type of walk)
'expert performed outside space' is the wordplay.
'expert' becomes 'pro' (short for professional).
'performed' becomes 'made' (I've seen this before).
'outside' indicates putting letters inside (some letters go outside others).
'space' becomes 'en' (in printing, a space as wide as a letter 'n').
'made' enclosing 'en' is 'menade'.
'pro'+'menade'='PROMENADE'
(Other definitions for promenade that I've seen before include "Seaside walk?" , "Seafront walk" , "Esplanade" , "Place for strolling by the sea" , "dance" .)