Juvenile paper's lead: 'Advice can be pretentious, in a manner of speaking'
I believe the answer is:
la-di-da
'juvenile' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I can't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for la-di-da that I've seen before include "Informally, having affected manner of pronunciation" , "Hoity-toity" , "Pretentious, snobbish" , "Affectedly genteel" , "I'd a lad with affected manner or pronunciation" .)