Outside latrine ultimately leads to sludge (5)
I believe the answer is:
slime
'to sludge' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for slime that I've seen before include "Sludge, gloop" , "Nasty slippery stuff" , "Gooey seeping stuff" , "could make things sticky" , "Slippery mud; slug trail" .)