Light cake (6)
I believe the answer is:
sponge
'light cake' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sponge that I've seen before include "marine life?" , "something to eat" , "Cadge - porous object used for washing" , "Piece of porous rubber" , "'Porous, absorbent substance (6)'" .)