Trustworthy Lib creed rewritten (8)
I believe the answer is:
credible
'trustworthy' is the definition.
(I've seen this in another clue)
'lib creed rewritten' is the wordplay.
'rewritten' indicates an anagram.
'lib'+'creed'='libcreed'
'libcreed' with letters rearranged gives 'CREDIBLE'.
(Other definitions for credible that I've seen before include "Convincing" , "Seemingly worthy of belief" , "Possible to believe" , "Within the bounds of belief" , "Believable - reliable" .)