Star of professional golf (5)
I believe the answer is:
algol
'star' is the definition.
(I know that Algol is a binary)
'of professional golf' is the wordplay.
'of' says the answer is hidden in the clue.
'ALGOL' is hidden within 'professional golf'.
(Other definitions for algol that I've seen before include "Computer language" , "Star" , "language (but not used in speech)" .)