Permeable by fluids (6)
I believe the answer is:
porous
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">permeable by fluids</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 porous that I've seen before include "Letting liquid or gas pass" , "Like a leaky field" , "Allowing air/liquid to pass through" , "Permeable to water etc" , "Not resistant to water" .)