More determined European takes husband's place in Elizabeth Castle's Jersey Shore home (8)

'more determined' is the definition.
(steely can mean determined)

'place in elizabeth castle's jersey shore home' is the wordplay.
'place' becomes 'tee' (teeing is a kind of placing).
'in' means one lot of letters goes inside another.
'elizabeth castle's jersey shore home' becomes 'slier' (I can't explain this - if you can you should give a lot more credence to this answer).
'tee' put within 'slier' is 'STEELIER'.

'european takes husband's' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.