Move like sludge (4)
I believe the answer is:
ooze
'move like sludge' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ooze that I've seen before include "Emit" , "Trickle slowly out, like mud" , "River-bed mud; leak slowly" , "Seep out slowly" , "Exude mud" .)