Is bright, that's obvious (5)
I believe the answer is:
clear
I believe this clue is a double definition.
'is bright' is the first definition.
(thesaurus)
'obvious' is the second definition.
('clear' can be similar in meaning to 'obvious')
'that's' is the link.
(Other definitions for clear that I've seen before include "Lucid, obvious" , "With no jams" , "Understandable" , "Set free of charges" , "Free from blame" .)