Baseball field (7)
I believe the answer is:
diamond
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">baseball field</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for diamond that I've seen before include "Carbon gem" , "Suit-baseball field - gem" , "Hard precious stone" , "Birthstone for April" , "Precious stone for mad Odin" .)