Like some goose egg good and ancient (6)
I believe the answer is:
golden
'like some goose egg' is the definition.
(as in the Goose that Laid the Golden Eggs)
'good and ancient' is the wordplay.
'good' becomes 'g' (abbreviation).
'and' is a charade indicator (letters next to each other).
'ancient' becomes 'olden' (as in the olden days).
'g'+'olden'='GOLDEN'
(Other definitions for golden that I've seen before include "50th Jubilee" , "Gilded, pale yellow" , "Autumnal flower" , "Brilliant" , "In Woodstock we are this" .)