I know I want to hear from you concerning a certain something (4,2,5,2)
I believe the answer is:
tell me about it
'i know' is the definition.
('tell me about it' means 'I know' or 'I agree')
'i want to hear from you concerning a certain something' is the wordplay.
I cannot really understand how this works, but
'from' could be 'o' (I've seen this in other clues) and 'o' is located in the answer.
'you' could be 'u' (homophones) and 'u' is located in the answer.
'a' is found in the answer.
'something' could be 'it' (both can refer to an object) and 'it' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tell me about it that I've seen before include "it is the usual problem" , "I need to know" , "I want to learn from you about computers and things" .)