Xmas booze g-g-gone astray! (6)
I believe the answer is:
eggnog
'xmas booze' is the definition.
(drink often drunk at Christmas)
'g-g-gone astray' is the wordplay.
'g-g-gone' becomes 'g-ggone' ('ggone' said with a stutter like 'g-gone' was; 'gone' said with a stammer like 'gone' was).
'astray' is an anagram indicator.
'gggone' with letters rearranged gives 'EGGNOG'.
(Other definitions for eggnog that I've seen before include "A punch for bedtime, perhaps" , "Alcohol-based drink" , "Kind of sweet punch" , "Christmas tipple" , "Winter cocktail" .)