To many, I'm not very clever (3)
I believe the answer is:
dim
'very clever' is the definition.
I can't judge whether this defines the answer.
'to many i'm' is the wordplay.
'to many' becomes 'd' (Roman numeral for 500).
'd'+'im'='DIM'
'not' acts as a link.
Can you help me to learn more?
(Other definitions for dim that I've seen before include "Unintelligent; badly lit" , "Lacking clarity or distinctness" , "Slow to learn" , "Somewhat out of sight" , "Opaque, not bright" .)