Dismissed just without reservation (8)
I believe the answer is:
outright
'without reservation' is the definition.
(I've seen this before)
'dismissed just' is the wordplay.
'dismissed' becomes 'out' (I've seen this before).
'just' becomes 'right' ('right' can be similar in meaning to 'just').
'out'+'right'='OUTRIGHT'
(Other definitions for outright that I've seen before include "Directly; without reservation" , "Complete; immediately" , "without qualifications" , "Without qualification" , "Completely - undisputed" .)