Freely available (2,3)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">freely available</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for on tap that I've seen before include "Where to find a washer" , "Constantly available like beer from keg" , "kept in a cask" , "Available whenever needed" , "Ready to be drawn off, say beer" .)
(Another definition for ontap that I've seen is " readily available".)