Ignorant solver can't do anything with such a crossword (8)
I believe the answer is:
clueless
I believe this is a double definition.
'ignorant' is the first definition.
(I've seen this before)
'solver can't do anything with such a crossword' is the second definition.
(cryptic definition)
(Other definitions for clueless that I've seen before include "Completely at sea about what's going on" , "not like our solvers!" , "Totally uninformed about what's going on" , "Stupid (unlike crosswords!)" , "such a crossword can't be solved!" .)