I’m surprised by US soldier’s dog (5)
I believe the answer is:
corgi
'dog' is the definition.
(corgi is a kind of dog)
'i'm surprised by us soldier's' is the wordplay.
'i'm surprised' becomes 'cor' (old-fashioned UK expression of shock or awe).
'by' is a charade indicator (letters next to each other).
'us soldier' becomes 'GI' (GI can mean an American soldier).
'cor'+'gi'='CORGI'
(Other definitions for corgi that I've seen before include "Barker?" , "found in the kennels" , "Dog of Welsh breed, royal favourite" , "Welsh 11" , "The Queen's favourite?" .)