Cookie that's readily stackable

OREO

["Think of a popular treat that often finds itself in tall towers."]

The clue "Cookie that's readily stackable" leads to the answer "OREO" through a straightforward description of the cookie's characteristic. Oreos are well-known for their flat, round shape and cream filling, which makes them easy to stack on top of each other. The phrase "readily stackable" hints at this physical property of Oreos, making them a good fit for the clue. There's no complex wordplay or pun involved; it's a direct reference to the popular cookie's stackable nature.