Understood to be fake (7)
I believe the answer is:
assumed
This clue is a double definition.
'understood' is the first definition.
('assumed' can be a synonym of 'understood')
'be fake' is the second definition.
(thesaurus)
'to' acts as a link.
(Other definitions for assumed that I've seen before include "Took for granted" , "Bogus" , "False" , "Took (control)" , "Surmised" .)