Live in sun during retirement (5)
I believe the answer is:
exist
'live' is the definition.
(synonyms)
'sun during retirement' is the wordplay.
'sun' becomes 's'.
'during' indicates putting letters inside.
'retirement' becomes 'exit' (I've seen this in other clues).
's' placed inside 'exit' is 'EXIST'.
'in' is the link.
(Other definitions for exist that I've seen before include "Get a life!" , "Scrape by" , "Live" , "Survive" , "Have objective reality" .)