Part of the foot and chin broken (4)
I believe the answer is:
inch
'part of the foot' is the definition.
('inch' is part of 'foot')
'chin broken' is the wordplay.
'broken' indicates anagramming the letters.
'chin' is an anagram of 'INCH'.
'and' acts as a link.
(Other definitions for inch that I've seen before include "2.54cm" , "Small measurement unit of distance" , "Move by small amounts" , "Part of a foot" , "Imperial unit of length" .)