Old folk freeze at home in retirement (5)
I believe the answer is:
iceni
'old folk' is the definition.
(ancient tribe of Britain)
'freeze at home in retirement' is the wordplay.
'freeze' becomes 'ice' (as in water turning into ice).
'at home' becomes 'in' (similar in meaning).
'in retirement' is a reversal indicator (retire can mean to go back or backwards).
'in' back-to-front is 'ni'.
'ice'+'ni'='ICENI'
(Other definitions for iceni that I've seen before include "Ancient Brits" , "Old people" , "British people once" , "Rebellious tribe" , "Very old folk" .)