A monster to make go back again (4)
I believe the answer is:
ogre
'a monster' is the definition.
(fairy tale monster)
'go back again' is the wordplay.
'back' says the letters should be written backwards.
'again' becomes 're' (prefix meaning 'again').
'go' back-to-front is 'og'.
'og'+'re'='OGRE'
'to make' is the link.
(Other definitions for ogre that I've seen before include "Bugbear" , "terrible person" , "Giant of folklore who ate humans" , "Monstrous creature" , "Giant who eats people" .)