Dull, uninteresting (13)
I believe this is a double definition.
'dull' is the first definition.
(similar in meaning)
'uninteresting' is the second definition.
(I've seen this in another clue)
(Other definitions for bland that I've seen before include "Insipid; lacklustre" , "Insipid, vapid" , "Dull - tasteless" , "without distinctive characteristics" , "Unruffled but unstimulating" .)
(Other definitions for characterless that I've seen before include "Dull" , "Lacking distinctive qualities" , "Nondescript" , "Lacking a distinctive nature" .)