Spacious, extensive (4)
I believe the answer is:
wide
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">spacious</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">extensive</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ ></span>
(Other definitions for wide that I've seen before include "Far from the mark" , "roomy" , "lax in morals" , "Unplayable ball (cricket)" , "Spacious; an extra" .)