Pigment sounds more likely to ooze (5)
I believe the answer is:
sepia
'pigment' is the definition.
(sepia is a kind of pigment)
'sounds more likely to ooze' is the wordplay.
'sounds' shows a homophone (sound like).
'more likely to ooze' becomes 'seepier' (more likely to seep).
'seepier' is a homophone of 'SEPIA'.
(Other definitions for sepia that I've seen before include "Reddish-brown; cuttlefish ink" , "Reddish-brown colour as in old photos" , "A greyish brown" , "Brownish tint or pigment" , "Reddish brown -- ie sap (anag)" .)