Heading off on piste, broke part of foot (6)
I believe the answer is:
instep
'part of foot' is the definition.
(I've seen this before)
'heading off on piste broke' is the wordplay.
'heading off' means to remove the first letter.
'broke' indicates anagramming the letters.
'on'+'piste'='onpiste'
'onpiste' with its initial letter taken away is 'npiste'.
'npiste' is an anagram of 'INSTEP'.
(Other definitions for instep that I've seen before include "Part of foot between toes and ankle" , "Part of foot/shoe" , "Set pin in part of foot" , "Section of foot" , "Sir Jack --, famous English cricketer" .)