Official authorisation (9)
I believe the answer is:
clearance
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">official authorisation</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for clearance that I've seen before include "Permission to proceed" , "OK" , "Vacation" , "Sanction" , "Green light" .)