Figure I'm not very bright (3)
I believe the answer is:
dim
'not very bright' is the definition.
(dim means poorly lit)
'figure i'm' is the wordplay.
'figure' becomes 'd' (I can't justify this - if you can you should give a lot more credence to this answer).
'd'+'im'='DIM'
Can you help me to learn more?
(Other definitions for dim that I've seen before include "Providing little light" , "Not bright, cloudy" , "out of mind?" , "Without much light" , "Not bright, literally or mentally" .)