Not liquid or solid (7)
I believe the answer is:
gaseous
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not liquid or solid</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for gaseous that I've seen before include "Not solid or liquid" , "lacking definition?" , "Like hydrogen" , "Like oxygen, neon, etc" , "Like helium" .)