Ad-lib (9)
I believe the answer is:
improvise
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ad-lib</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that ad-lib can be written as improvise)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for improvise that I've seen before include "Extemporise" , "Talk without notes" , "Create without preparation" , "Use whatever materials are to hand" , "Ad-lib" .)