Hoax over rubbish presented as decree (6)
I believe the answer is:
diktat
'decree' is the definition.
(I've seen this before)
'hoax over rubbish presented' is the wordplay.
'hoax' becomes 'kid'.
'over' is a reversal indicator.
'rubbish' becomes 'tat' (low-quality items or material).
'presented' means one lot of letters go next to another.
'kid' written backwards gives 'dik'.
'dik'+'tat'='DIKTAT'
'as' is the link.
(Other definitions for diktat that I've seen before include "Categorical decree" , "Decree imposed from above" , "Categorical statement" , "Official order" , "imposed order" .)