Remaining untruthful (5)
I believe the answer is:
lying
This clue is a double definition.
'remaining' is the first definition.
(lie can mean to remain or stay)
'untruthful' is the second definition.
(similar in meaning)
(Other definitions for lying that I've seen before include "dishonesty" , "Mendacious; recumbent" , "Matilda's behaviour" , "retailing pork pies" , "Untruthful - in bed?" .)