Some terrible mishap results in a scar (7)
I believe the answer is:
blemish
'a scar' is the definition.
(thesaurus)
'some terrible mishap results' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'BLEMISH' can be found hidden inside 'terrible mishap results'.
'in' is the link.
(Other definitions for blemish that I've seen before include "Small flaw" , "Stain - defect" , "bad mark?" , "deformity" , "Stain, flaw" .)