Better returning by end of space walk! (4)
I believe the answer is:
pace
'walk' is the definition.
(pacing is a kind of walking)
'better returning by end of space' is the wordplay.
'better' becomes 'cap' (I've seen this before).
'returning' says the letters should be written backwards.
'by' is a charade indicator (letters next to each other).
'end of' suggests the final letters.
The last letter of 'space' is 'e'.
'cap' written backwards gives 'pac'.
'pac'+'e'='PACE'
(Other definitions for pace that I've seen before include "With due respect" , "a certain distance" , "Part of step" , "speed of movement" , "Rate of progress" .)