Removing half of moat crossing: that's elevation! (5)
I believe the answer is:
ridge
'elevation' is the definition.
(ridge is a kind of elevation)
'removing half of moat crossing' is the wordplay.
'removing half of' means to take half the letters.
'moat crossing' becomes 'drawbridge'.
'drawbridge' cut in half is 'RIDGE'.
'that's' acts as a link.
(Other definitions for ridge that I've seen before include "Long narrow crest" , "A narrow raised strip in bridges" , "Wrinkle" , "Rooftop" , "Raised crease" .)