Bill backed by minister, it’s true (8)
I believe the answer is:
accurate
'true' is the definition.
(similar in meaning)
'bill backed by minister' is the wordplay.
'bill' becomes 'ac' (short for account).
'backed by' is a charade indicator (letters next to each other).
'minister' becomes 'curate' (synonyms).
'ac'+'curate'='ACCURATE'
'it's' is the link.
(Other definitions for accurate that I've seen before include "telling it like it is" , "Totally correct" , "Precise and exact (8)" , "True!" , "Meticulous" .)