A flat rise also (5)

I believe the answer is:

level

I'm a little stuck... Click here to teach me more about this clue!

'a flat' is the definition.
(I know that flat can be written as level)

I can't explain the rest of the clue.

(Other definitions for level that I've seen before include "Flat, even" , "Flush" , "Having a flat, horizontal surface" , "Palindromic tier?" , "Regular" .)

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