Noble support, one hears (4)
I believe the answer is:
peer
'noble' is the definition.
(peers are members of the nobility)
'support one hears' is the wordplay.
'support' becomes 'pier' (type of structure).
'one hears' shows a homophone (sound like) (I've seen 'heard' mean this).
'pier' sounds like 'PEER'.
(Other definitions for peer that I've seen before include "Gaze" , "Member of the nobility" , "Noble; look with difficulty" , "One's equal" , "Look closely at equal" .)