Terrible liar not appearing in court (2,5)
I believe the answer is:
on trial
'in court' is the definition.
(I've seen this before)
'terrible liar not' is the wordplay.
'terrible' indicates anagramming the letters.
'liar'+'not'='liarnot'
'liarnot' anagrammed gives 'ON TRIAL'.
'appearing' acts as a link.
(Other definitions for on trial that I've seen before include "Undergoing scrutiny" , "heard?" , "before the judge" , "In court to answer charge, in the dock" , "In court to answer charges" .)