In short supply (6)
(Other definitions for sparse that I've seen before include "Rare" , "Thinly dotted about" , "One's not at all thick" , "rarely occurring" , "Thin on the ground, scarce" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">in short supply</span>' is the definition.<br/ ><span class="explanation-format__explanation">(both can mean rare)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for scarce that I've seen before include "Not enough to meet demand" , "Hard to obtain" , "Not plentiful, in short supply" , "Rare shock Conservative getting in" , "Common? Definitely not" .)