Sponge feature (4)
I believe the answer is:
pore
'sponge feature' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pore that I've seen before include "Tiny opening in the skin" , "Minute passage in skin" , "Closely study" , "Rope around the skin-opening" , "Small hole" .)