Lack of difficulty heartens edgy teenager completing puzzle (6)
I believe the answer is:
teaser
'puzzle' is the definition.
(I've seen this before)
'lack of difficulty heartens edgy teenager completing' is the wordplay.
I cannot really see how this works, but
'lack' could be 'ease' (I have seen 'Lack of difficulty ' mean 'ease' so perhaps 'lack' could also mean 'ease') and 'ease' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for teaser that I've seen before include "Introduction to arouse curiosity" , "Tricky question; intriguing preliminary advert" , "One who annoys people or cards wool" , "Riddle" , "inducement" .)