Curved foot part (4)
I believe the answer is:
arch
'curved foot part' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for arch that I've seen before include "Curved overhead structure" , "Vaulted opening" , "Way though - on foot!" , "Masonry construction for spanning an opening" , "Curved part of stone bridge, perhaps" .)