Metal support poles (5)
I believe the answer is:
brass
'metal' is the definition.
(brass is a kind of metal)
'support poles' is the wordplay.
'support' becomes 'bra' (a support for the breasts).
'poles' becomes 'ss' (I am not sure about this - if you are sure you should believe this answer much more).
'bra'+'ss'='BRASS'
Can you help me to learn more?
(Other definitions for brass that I've seen before include "Alloy of Cu and Zn" , "Boldness" , "some musicians!" , "Baggage" , "It's there, if muck's there" .)