Mandible or maxilla (4)
I believe this is a double definition.
'mandible' is the first definition.
(synonyms)
'maxilla' is the second definition.
(I've seen this before)
(Other definitions for jawbone that I've seen before include "Samson smote enemies with the . . . . . . . of an ass" , "Mandible" , "A new job (anag.)" , "It's hinged to allow the mouth to open" , "Maxilla" .)
I believe this clue is a double definition.
'mandible' is the first definition.
(thesaurus)
'maxilla' is the second definition.
(thesaurus)
(Other definitions for bone that I've seen before include "Skeleton component" , "It makes up the skeleton" , "How dry" , "#Close to it is risque" , "Skeletal segment" .)