King to love English deer (3)
I believe the answer is:
roe
'deer' is the definition.
(roe deer is a kind of deer)
'king to love english' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'to love' becomes 'o' (love means zero in tennis).
'english' becomes 'e' (abbreviation).
'r'+'o'+'e'='ROE'
(Other definitions for roe that I've seen before include "Mass of fish eggs" , "Caviar" , "Lobster's ripe ovary" , "Mass of fish's eggs" , "shy animal" .)