Self-willed (10)
I believe the answer is:
headstrong
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">self-willed</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that self-willed can be written as headstrong)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for headstrong that I've seen before include "Showing wilfulness" , "Wilfully determined" , "Wilful, determined" , "obstinately self-willed" , "pig-headed" .)