Unaccompanied, alone (4)
I believe the answer is:
solo
I believe this is a double definition.
'unaccompanied' is the first definition.
(I know that unaccompanied can be written as solo)
'alone' is the second definition.
(as in a musical solo)
(Other definitions for solo that I've seen before include "Unaccompanied flight" , "Unaccompanied passage" , "It's performed alone" , "By oneself" , "Done by one person" .)