Advances slowly (6)
I believe the answer is:
creeps
(Other definitions for creeps that I've seen before include "Unpleasantly strange people" , "'Tomorrow, and tomorrow, and tomorrow / . . . . . . in this petty place from day to day' (Macbeth)" , "21 [SNAKES]" , "feeling of revulsion" , "Moves slowly and stealthily" .)