Cul-de-sac (4,3)
I believe the answer is:
dead end
'cul-de-sac' is the definition.
(synonyms)
This is all the clue.
(Other definitions for dead end that I've seen before include "A blind alley, sounds moribund" , "Blind alley or situation without prospects" , "Impasse" , "Blind alley, cul-de-sac" , "that's leading nowhere" .)