Dawn -- possibly after escort will suspiciously disappear (4,6,5)
I believe the answer is:
take french leave
'dawn' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'after escort will suspiciously disappear' is the wordplay.
'after' means one lot of letters go next to another.
'escort' becomes 'take' (both can mean to guide or accompany someone).
'will suspiciously' becomes 'french' (I can't justify this - if you can you should believe this answer much more).
'disappear' becomes 'leave'.
'take' next to 'french' is 'takefrench'.
'takefrench'+'leave'='TAKE FRENCH LEAVE'
'possibly' is the link.
Can you help me to learn more?
(Other definitions for take french leave that I've seen before include "depart unannounced" , "Disappear without permission" .)