Platitude with unusually morbid note (7)
I believe the answer is:
bromide
'platitude' is the definition.
('bromide' can be a synonym of 'platitude')
'with unusually morbid note' is the wordplay.
'with' is a charade indicator (letters next to each other).
'unusually' indicates an anagram.
'note' becomes 'e' (musical note).
'morbid' is an anagram of 'bromid'.
'bromid' next to 'e' is 'BROMIDE'.
(Other definitions for bromide that I've seen before include "that could send you to sleep?" , "Trite fob-off" , "Trite remark" , "Platitude" , "Dim bore (anag.)" .)