One island, rocky, but not a dangerous place (5,3)
I believe the answer is:
lions den
'one island rocky but' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'a dangerous place' is the wordplay.
'a dangerous' becomes 'lions' (I can't justify this - if you can you should give a lot more credence to this answer).
'place' becomes 'den' (den is a kind of place).
'lions'+'den'='LIONS' DEN'
'not' acts as a link.
Can you help me to learn more?
(Another definition for lions den that I've seen is " Danger spot survived by Daniel".)