Son leaves Harry Potter's rabbit (5)
I believe the answer is:
peter
'potter's rabbit' is the definition.
(I've seen this in another clue)
'son leaves harry' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'leaves' suggests deleting specific letters.
'harry' becomes 'pester' (both can mean to bother).
'pester' with 's' taken away is 'PETER'.
(Other definitions for peter that I've seen before include "Leader of the Apostles" , "Sir - - Ustinov" , "prison cell" , "- Grimes (Britten)" , "Apostle - saint - first Pope?" .)