Sponge saddle cover? (3)
I believe the answer is:
bum
I believe this clue is a double definition.
'sponge' is the first definition.
(I know that sponge can be written as bum)
'saddle cover?' is the second definition.
(eg a cyclist's behind goes on a saddle)
(Other definitions for bum that I've seen before include "Layabout" , "Begging" , "American tramp or English bottom" , "American hobo or vulgar bottom" , "Behind" .)