Remove restraint if at intervals some distance back (9)
I believe the answer is:
eliminate
'remove' is the definition.
(I know that eliminate is a more specific form of the action remove)
'restraint if at intervals some distance back' is the wordplay.
'at intervals' indicates alternate letters (letters are taken at regular intervals).
'some distance' becomes 'mile' (mile is a unit of distance).
'back' shows that the letters should be reversed in order.
'restraint'+'if'='restraintif'
The alternating letters of 'restraintif' are 'etani'.
'etani'+'mile'='etanimile'
'etanimile' reversed gives 'ELIMINATE'.
(Other definitions for eliminate that I've seen before include "Exclude from further stage of competition" , "Do away with, remove" , "put out" , "Take out" , "Completely remove, get rid of" .)