Joint work brought back large animal (5)
I believe the answer is:
hippo
'large animal' is the definition.
(I've seen this before)
'joint work brought back' is the wordplay.
'joint' becomes 'hip' (part of body).
'work' becomes 'op' (common abbreviation for 'opus').
'brought back' is a reversal indicator.
'op' in reverse letter order is 'po'.
'hip'+'po'='HIPPO'
(Other definitions for hippo that I've seen before include "Augustine looked after" , "African wallower (abbr)" , "Large animal" , "large African creature" , "Aquatic creature" .)