End of crossword — I am needing a bit of illumination? (3)
I believe the answer is:
dim
'needing a bit of illumination?' is the definition.
(dim means lacking light)
'end of crossword i am' is the wordplay.
'end of' indicates one should take the final letters.
'i am' becomes 'i'm'.
The last letter of 'crossword' is 'd'.
'd'+'im'='DIM'
(Other definitions for dim that I've seen before include "Not bright, cloudy" , "Slow-witted" , "Not bright, shadowy" , "Gloomy; dull" , "Lose brightness" .)