Act like a snake (7)
I believe the answer is:
slither
'act like a snake' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for slither that I've seen before include "Move like a snake" , "Slide on slippery surface" , "Slide (like a snake)" , "Move smoothly over a surface with a twisting motion" , "Slide unsteadily" .)