Permeable by fluids (6)
I believe the answer is:
porous
'permeable by fluids' is the definition.
(I've seen this before)
This is all the clue.
(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" .)