Brain, slangily (6)
I believe the answer is:
noodle
'brain slangily' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for noodle that I've seen before include "Fool (in the soup?)" , "Ribbon strip of pasta" , "In slang, a foolish person or just the head" , "Goose" , "Form of pasta" .)