Returned therefore to see Shrek, perhaps (4)
I believe the answer is:
ogre
'shrek perhaps' is the definition.
(the film character Shrek is an ogre)
'returned therefore' is the wordplay.
'returned' is a reversal indicator.
'therefore' becomes 'ergo' (I've seen this before).
'ergo' in reverse letter order is 'OGRE'.
'to see' is the link.
(Other definitions for ogre that I've seen before include "Human-eating giant" , "'Demon, fiend (4)'" , "Giant of folklore who liked to eat humans" , "Ergo (anag.)" , "Bogeyman" .)