Set broken leg (3)
I believe the answer is:
gel
'set' is the definition.
(both can mean to harden)
'broken leg' is the wordplay.
'broken' indicates an anagram.
'leg' anagrammed gives 'GEL'.
(Other definitions for gel that I've seen before include "Thicken" , "shock application?" , "shock treatment" , "It may be applied to locks" , "Hair treatment" .)