Endlessly difficult idiot making trouble (6)
I believe the answer is:
harass
'trouble' is the definition.
(I've seen this before)
'endlessly difficult idiot making' is the wordplay.
'endlessly' means to remove the last letter.
'difficult' becomes 'hard' (associated in meaning).
'idiot making' becomes 'ass' (I can't justify this - if you can you should give a lot more credence to this answer).
'hard' with its final letter taken off is 'har'.
'har'+'ass'='HARASS'
Can you help me to learn more?
(Other definitions for harass that I've seen before include "Disturb < badger" , "Trouble constantly" , "Make repeated attacks on" , "Pester, annoy continually (6)" , "Badger, antagonise" .)