I'm not sure interrupting idiots is prejudicial (7)
I believe the answer is:
assumes
'is prejudicial' is the definition.
I can't tell whether this defines the answer.
'i'm not sure interrupting idiots' is the wordplay.
'i'm not sure' becomes 'um' (expression of hesitation).
'interrupting' is an insertion indicator.
'idiots' becomes 'asses' (I've seen this before).
'um' going within 'asses' is 'ASSUMES'.
Can you help me to learn more?
(Other definitions for assumes that I've seen before include "Takes for granted or puts on" , "Takes to be the case" , "dons" , "Puts on; accepts" , "Take to be the case" .)