Chain's not broken for support (9)
I believe the answer is:
stanchion
'for support' is the definition.
(stanchion is a kind of support)
'chain's not broken' is the wordplay.
'broken' is an anagram indicator.
'chains'+'not'='chainsnot'
'chainsnot' anagrammed gives 'STANCHION'.
(Other definitions for stanchion that I've seen before include "Vertical post or rod as a support" , "Upright" , "Post or rod used as a support" .)