Way to put down or flatter animal, maybe (8)
I believe the answer is:
roadkill
'flatter animal maybe' is the definition.
(animal flattened by a vehicle)
'way to put down' is the wordplay.
'way' becomes 'road' (road is a kind of way).
'to put down' becomes 'kill' (put down can mean to kill).
'road'+'kill'='ROADKILL'
'or' acts as a link.
(Other definitions for roadkill that I've seen before include "A passing motoring phenomenon" , "Creatures squashed on the motorway?" , "Animal slain by cars" , "Animals slain by vehicles" .)