Badly rusts framework (5)
I believe the answer is:
truss
'framework' is the definition.
(I know that truss is a type of framework)
'badly rusts' is the wordplay.
'badly' indicates anagramming the letters.
'rusts' with letters rearranged gives 'TRUSS'.
(Other definitions for truss that I've seen before include "Surgical appliance" , "Bundle of hay or straw" , "Padded device worn to support a hernia" , "Supporting framework" , "Architectural corbel" .)