Elevation makes fourth architect sick (4)
I believe the answer is:
hill
'elevation' is the definition.
(hill is a kind of elevation)
'fourth architect sick' is the wordplay.
'fourth architect' becomes 'h' (4th letter of 'architect').
'sick' becomes 'ill' (synonyms).
'h'+'ill'='HILL'
'makes' is the link.
(Other definitions for hill that I've seen before include "Mount" , "See 14" , "Over the .... - past life's prime" , "Fell" , "pike" .)