Microsoft search engine (4)
I believe the answer is:
bing
'microsoft search engine' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bing that I've seen before include "Sobriquet of Harry Lillis Crosby" , "The Old Groaner" , "Daddy of the crooners . . . . Crosby" , "-- Crosby, singer" .)