Soldier rejected champagne brand with expression of surprise (6)
I believe the answer is:
gurkha
'soldier' is the definition.
(term for a Nepalese soldier of the British Army)
'rejected champagne brand with expression of surprise' is the wordplay.
'rejected' is a reversal indicator.
'champagne brand' becomes 'krug' (Krug is a French champagne brand).
'with' means one lot of letters go next to another.
'expression of surprise' becomes 'ha'.
'krug' written backwards gives 'gurk'.
'gurk'+'ha'='GURKHA'
(Other definitions for gurkha that I've seen before include "military type?" , "Nepalese fighter?" , "British soldier recruited overseas" , "I may be recruited" , "Highland warrior" .)