Join as private, one sent out (6)
I believe the answer is:
solder
'join' is the definition.
(I know that solder is a kind of join)
'as private one sent out' is the wordplay.
I cannot quite see how this works, but
'as' could be 'so' (I've seen this in other clues) and 'so' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for solder that I've seen before include "Join or fuse metal, using an alloy" , "Join two metal surfaces, using an alloy" , "Metal bond" , "Melted alloy, used to join two metal surfaces" , "Join two metal surfaces together" .)