Broken arm support (5)
I believe the answer is:
sling
'broken arm support' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sling that I've seen before include "Throw, fling" , "Bandage support; hurl" , "Catapult - shoe - support" , "Catapult or support as for injured arm" , "Chuck; support for damaged arm" .)