Utilisation (5)
I believe the answer is:
usage
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">utilisation</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that utilisation can be written as usage)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for usage that I've seen before include "etiquette" , "Interest of old" , "Style of language" , "Established custom" , "Customary way in which language is spoken or written" .)