Doctor's sign (7)
I believe the answer is:
shingle
'doctor's sign' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for shingle that I've seen before include "A tile; some beach" , "Here one comes close to the main" , "Mass of small rounded pebbles" , "Small worn stones and pebbles on the shore" , "Collection of stones" .)