Many cited terrible untruthfulness (9)
I believe the answer is:
mendacity
'untruthfulness' is the definition.
(mendacity is a kind of untruthfulness)
'many cited terrible' is the wordplay.
'terrible' is an anagram indicator.
'many'+'cited'='manycited'
'manycited' is an anagram of 'MENDACITY'.
(Other definitions for mendacity that I've seen before include "Quality or habit of telling lies or being deceitful" , "Lying" , "Untruthfulness" .)