Flat in Stevenage (4)
I believe the answer is:
even
'flat' is the definition.
(level)
'in stevenage' is the wordplay.
'in' indicates the answer is hidden within the clue.
'EVEN' can be found hidden inside 'stevenage'.
(Other definitions for even that I've seen before include "Flat, regular" , "Not odd; flat" , "Flat, smooth and divisible by two" , "Commensurate" , "Like half the numbers" .)