Berlin agreement to protect tailless wild cat (6)
I believe the answer is:
jaguar
'wild cat' is the definition.
(I've seen this before)
'berlin agreement to protect tailless' is the wordplay.
'berlin agreement' becomes 'ja' (German for yes).
'to protect' becomes 'guard' (guarding is a kind of protecting).
'tailless' means to remove the last letter.
'guard' with its final letter taken off is 'guar'.
'ja'+'guar'='JAGUAR'
(Other definitions for jaguar that I've seen before include "Large cat of tropical America, or fast car" , "Big cat of tropical America" , "Largest American big cat" , "Car marque and big cat" , "Spotted feline and prestigious car" .)