Deserter held by U.S. soldiery without charge (6)
I believe the answer is:
gratis
'without charge' is the definition.
(I've seen this in another clue)
'deserter held by u s soldiery' is the wordplay.
'deserter' becomes 'rat' (both can mean a traitor).
'held by' indicates putting letters inside.
'u s soldiery' becomes 'gis' (I can't justify this - if you can you should give a lot more credence to this answer).
'rat' inserted inside 'gis' is 'GRATIS'.
Can you help me to learn more?
(Other definitions for gratis that I've seen before include "Costing nothing, free" , "Free, at no cost" , "Without payment" , "Without charge" , "Free, costs nothing" .)