Old people, about fifty, in shrine (6)
I believe the answer is:
oracle
'shrine' is the definition.
(oracle is a kind of shrine)
'old people about fifty' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'people' becomes 'race'.
'about' indicates putting letters inside.
'fifty' becomes 'l' (roman numeral).
'race' going around 'l' is 'racle'.
'o'+'racle'='ORACLE'
'in' is the link.
(Other definitions for oracle that I've seen before include "Voice of god" , "O, clear off for the Greek wise man" , "Authoritative person who divines the future" , "One believed to give divinely-inspired answers" , "Ancient Greek expounder of wisdom" .)