I know a little, but emo is complicated (4,2,5,2)
I believe the answer is:
tell me about it
'i know' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'a little but emo is complicated' is the wordplay.
'is complicated' indicates an anagram (a complex or confusing ordering of the letters).
'a'+'little'+'but'+'emo'='alittlebutemo'
'alittlebutemo' is an anagram of 'TELL ME ABOUT IT'.
Can you help me to learn more?
(Other definitions for tell me about it that I've seen before include "I need to know" , "I want to learn from you about computers and things" , "it is the usual problem" .)