Composed note reviewing toilet (4)
I believe the answer is:
cool
'composed' is the definition.
(similar in meaning)
'note reviewing toilet' is the wordplay.
'note' becomes 'c' (musical note).
'reviewing' says the letters should be written in reverse (I've seen 'reviews' mean this (view the letters another way)).
'toilet' becomes 'loo' (loo can informally mean a toilet).
'loo' back-to-front is 'ool'.
'c'+'ool'='COOL'
(Other definitions for cool that I've seen before include "Sangfroid" , "Calm; chilly" , "Lose heat" , "Moderate" , "Neither warm nor very cold" .)