This person articulated key revelation (3-6)
I believe the answer is:
eye-opener
'revelation' is the definition.
(I have seen 'unexpected revelation' mean 'eye opener' so perhaps 'revelation' could also mean 'eye opener')
'this person articulated key' is the wordplay.
'this person' becomes 'I' (the person writing).
'articulated' shows a homophone (sound like).
'key' becomes 'opener' (I've seen this before).
'i' is a homophone of 'eye'.
'eye'+'opener'='EYE-OPENER'
(Other definitions for eye-opener that I've seen before include "Revelation or enlightenment - with optical reaction?" , "Unexpected revelation" , "Startling revelation" , "Startling thing" , "This surprises greatly - makes you look" .)