"Science Guy" Bill (3)
I believe the answer is:
nye
'science guy bill' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nye that I've seen before include "Nickname of Aneurin Bevan" , "- - Bevan (politics)" , "Flock of pheasants" , "- - Bevan (NHS pioneer)" , "- - Bevan, 13 dn" .)