Like a ratty piper (4)
I believe the answer is:
pied
'like' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I don't see?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for pied that I've seen before include "Foot over water [in]" , "varying in colour" , "black and white" , "With patches coloured differently" , "featuring two colours" .)