Dark end of dead end (5)
I believe the answer is:
drear
'dark' is the definition.
(I know that dark can be written as drear)
'end of dead end' is the wordplay.
'end of' suggests the final letters.
'end' becomes 'rear' (both can mean the back part of something).
The final letter of 'dead' is 'd'.
'd'+'rear'='DREAR'
(Other definitions for drear that I've seen before include "gloomy in poem" , "Dull and tedious" , "Morose" , "Poetic dull and uninteresting" , "miserable" .)