Like snakes, four having shed skin inside hole (7)
I believe the answer is:
sinuous
'like snakes four' is the definition.
Both the answer and definition are adjectives. Maybe you can see an association between them that I can't see?
'shed skin inside hole' is the wordplay.
I cannot really see how this works, but
'inside' could be 'in' and 'in' is located in the answer.
'hole' could be 'o' and 'o' is found within the answer.
This may be the basis of clue (or it may be nonsense).
'having' is the link.
Can you help me to learn more?
(Other definitions for sinuous that I've seen before include "Wavy -- winding" , "Snakelike" , "Curving in and out" , "Serpentine" , "Having many curves and turns" .)