Lacking bright ideas, I'm at a dead end (3)
I believe the answer is:
dim
'lacking bright ideas i'm at a dead end' is the definition.
I can't tell whether this defines the answer.
'i'm at a dead end' is the wordplay.
'at' says to put letters next to each other (I've seen this in other clues).
'end' suggests the final letters.
The final letter of 'dead' is 'd'.
'im' after 'd' is 'DIM'.
Can you help me to learn more?
(Other definitions for dim that I've seen before include "out of mind?" , "Unpromising" , "Sombre" , "Obscure, not bright" , "Providing little light" .)