Demure love note for wild beast (6)
I believe the answer is:
coyote
'wild beast' is the definition.
'demure love note' is the wordplay.
'demure' becomes 'coy' ('coy' can be a synonym of 'demure').
'love' becomes 'o' (In tennis, 'love' means 'zero').
'note' becomes 'te'.
'coy'+'o'+'te'='COYOTE'
'for' acts as a link.
(Other definitions for coyote that I've seen before include "Wolf-like wild dog" , "predatory creature" , "Small wild dog" , "Wild prairie dog in America" , "Wild canine" .)