TV's "Science Guy” Bill (3)
I believe the answer is:
nye
'tv's science guy bill' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nye that I've seen before include "So-called government minister" , "- Bevan, former Labour politician" , "- - Bevan, 13 dn" , "- - Bevan (politics)" , "Flock of pheasants" .)