Live in an old ruin at some stage (5)
I believe the answer is:
lodge
'live' is the definition.
(lodging is a kind of living)
'an old ruin at some stage' is the wordplay.
'ruin' indicates an anagram.
'at some stage' becomes 'ge' (I can't justify this - if you can you should give a lot more credence to this answer).
'old' is an anagram of 'lod'.
'lod'+'ge'='LODGE'
'in' is the link.
Can you help me to learn more?
(Other definitions for lodge that I've seen before include "Beaver's home - hunters use it!" , "Become firmly fixed" , "Masonic association" , "British physicist" , "next door to Mansion House?" .)