Melted mess (3)
I believe the answer is:
goo
'melted mess' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for goo that I've seen before include "Sentimentality (sl.)" , "Sticky gunge" , "Sticky matter" , "Anything sticky" , "Sticky stuff or sickly sentiment" .)