Science advocate Bill (3)
I believe the answer is:
nye
'science advocate 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 "Pheasant's nest" , "- - Bevan, 13 dn" , "- Bevan, former Labour politician" , "-- Bevan, NHS founder" , "Nickname of Aneurin Bevan" .)