Wild animal behaving with love to the end (5)
I believe the answer is:
dingo
'wild animal' is the definition.
(I've seen this before)
'behaving with love to the end' is the wordplay.
'behaving' becomes 'dio' (I am not sure about this - if you are sure you should believe this answer much more).
'with' indicates putting letters inside.
'love' becomes 'nothing' (love means zero in tennis).
'to the end' means to remove the middle letters (I've seen 'ends' mean this).
'nothing' with its centre removed is 'ng'.
'dio' enclosing 'ng' is 'DINGO'.
(Other definitions for dingo that I've seen before include "Yellow Australian dog" , "Wild Australian dog" , "Wild creature" , "Wild thing" , "Scavenger" .)