Clam soup (7)
I believe the answer is:
chowder
'clam soup' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for chowder that I've seen before include "dish in America" , "Thick soup containing clams or fish" , "possible first course?" , "Thick fish stew" , "Rich soup with fish, clams etc." .)