Open to all (6)
I believe the answer is:
public
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">open to all</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 public that I've seen before include "Offence against common decency" , "Open; not private" , "School or house" , "Overt" , "In open view" .)