Black-and-white seabird (3)
'black-and-white seabird' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for auk that I've seen before include "One that flies" , "Northern sea bird with short narrow wings" , "Black-and-white diving bird of northern seas" , "Black/white northern diver" , "A seabird from Milwaukee" .)
(Other definitions for razorbill that I've seen before include "flier" , "Type of auk" , "Bird" .)