What sounds like steep part of old England (4)
'what sounds like steep' is the definition.
I can't judge whether this defines the answer.
'part of old england' is the wordplay.
'part' becomes 'so' (so is a kind of part).
'of old' becomes 'k' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'england' becomes 'e'.
Can you help me to learn more?
(Another definition for soke that I've seen is "district under particular jurisdiction".)