Piece of shiny material to stretch across broken leg (7)
I believe the answer is:
spangle
'piece of shiny material' is the definition.
(sequin-like item on clothing)
'stretch across broken leg' is the wordplay.
'stretch' becomes 'span' (I've seen this before).
'across' means one lot of letters go next to another (across can mean on).
'broken' indicates an anagram.
'leg' is an anagram of 'gle'.
'span'+'gle'='SPANGLE'
'to' is the link.
(Other definitions for spangle that I've seen before include "Glittery item" , "Glittering ornament" , "Colourful spot" , "it glitters" , "metal plate" .)