Assure setter that as regards technology, I know exactly what you mean (4,2,5,2)
I believe the answer is:
tell me about it
'i know exactly what you mean' is the definition.
I know nothing about this answer so I can't judge whether this works.
'assure setter that as regards technology' is the wordplay.
'assure' becomes 'tell' (synonyms).
'setter' becomes 'me' (the setter of the clue).
'that as regards' becomes 'about' (I can't explain this - if you can you should believe this answer much more).
'technology' becomes 'IT' (Information Technology).
'tell'+'me'+'about'+'it'='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" .)