Brown arrived late without a note (5)
I believe the answer is:
camel
'brown' is the definition.
(camel is a shade of brown)
'arrived late without a note' is the wordplay.
'arrived late' becomes 'cl' (I can't justify this - if you can you should give a lot more credence to this answer).
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'note' becomes 'me'.
'a'+'me'='ame'
'cl' going around 'ame' is 'CAMEL'.
(Other definitions for camel that I've seen before include "Bearer of burdens" , "Light yellowish-brown colour - ruminant" , "Beast of burden in desert regions" , "Humped beast" , "Ungulate mammal" .)