Live in the past? I'd settle Thebes at first (5)
I believe the answer is:
exist
'live' is the definition.
('exist' can be a synonym of 'live')
'past? i'd settle thebes at first' is the wordplay.
'past?' becomes 'ex' ('ex' can be similar in meaning to 'past').
'at first' indicates taking the first letters.
The initial letters of 'id settle thebes' is 'ist'.
'ex'+'ist'='EXIST'
'in the' acts as a link.
(Other definitions for exist that I've seen before include "Survive" , "Subsist" , "Scrape by" , "Have being or continue living" , "Get a life!" .)