Curve hard to miss in part of a legislature (6)
I believe the answer is:
camber
'curve' is the definition.
(I know that camber is a more specific form of the action curve)
'hard to miss in part of a legislature' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'to miss in' suggests deleting specific letters.
'part of a legislature' becomes 'chamber' (eg the upper and lower chambers of a parliament).
'chamber' with 'h' taken away is 'CAMBER'.
(Other definitions for camber that I've seen before include "Slope on road surface" , "may appear on road" , "bend in road" , "Slight tilt" , "Slight convexity, like the surface of a road" .)