Beast in a police car? (5)
I believe the answer is:
panda
This clue is a double definition.
'beast' is the first definition.
(I've seen this before)
'a police car?' is the second definition.
(I've seen this before)
'in' acts as a link.
(Other definitions for panda that I've seen before include "Endangered bamboo eater" , "Black-eyed animal" , "Bamboo-eating mammal" , "One eating bamboo" , "Bamboo-eater" .)