BART part (4)
I believe the answer is:
area
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bart part</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for area that I've seen before include "Succession, order" , "Expanse of a surface" , "part of town" , "Region, space" , "Space for a specific purpose, say picnic" .)