Living in English castle somehow is a step up (8)
I believe the answer is:
escalate
'step up' is the definition.
('escalate' can be a synonym of 'step up')
'living in english castle somehow is a' is the wordplay.
'living in' means one lot of letters goes inside another.
'english' becomes 'e' (abbreviation).
'somehow' indicates an anagram.
'e'+'castle'='ecastle'
'ecastle' is an anagram of 'escalte'.
'escalte' placed around 'a' is 'ESCALATE'.
(Other definitions for escalate that I've seen before include "Amplify" , "rocket" , "Quickly increase in scale" , "mount in tension" , "Increase in intensity or extent, like trouble brewing" .)