Slam (into) (3)
I believe the answer is:
ram
'slam into' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ram that I've seen before include "Aries is the Sign of the ..." , "An animal; forcibly crash into" , "'Computer memory, initially (3)'" , "The constellation Aries" , "Thrust" .)