hard-nosed (10)
(Other definitions for headstrong that I've seen before include "Wilfully determined" , "strong-willed" , "obstinately self-willed" , "pig-headed" , "Obstinate" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hard-nosed</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for stern that I've seen before include "Grave; rear" , "Rear of a vessel" , "Forbidding, austere" , "Strict - forbidding" , "Forbidding in aspect" .)