Santa's vehicle breaks his leg (6)
I believe the answer is:
sleigh
'santa's vehicle' is the definition.
(I've seen this before)
'breaks his leg' is the wordplay.
'breaks' indicates anagramming the letters.
'his'+'leg'='hisleg'
'hisleg' anagrammed gives 'SLEIGH'.
(Other definitions for sleigh that I've seen before include "transport (with bells on!)" , "Dancer pulled this" , "13 ac's transport" , "Vehicle suitable for snow" , "Transport in winter" .)