Bring up the back (4)
I believe the answer is:
This clue is a triple definition!
'bring' is the first definition.
'up' is the second definition.
'the back' is the third definition.
(something's rear is its back)
(Other definitions for rear that I've seen before include "Rise up at the back" , "Hindmost part" , "Breed or bring up" , "Back; bring up (young)" , "Bring up (children)" .)