Magistrate, around Christmas, heading off for drink (5)
I believe the answer is:
julep
'for drink' is the definition.
(julep is a kind of drink)
'magistrate around christmas heading off' is the wordplay.
'magistrate' becomes 'jp'.
'around' means one lot of letters goes inside another.
'christmas' becomes 'yule' (Yule is the Christmas period).
'heading off' means to remove the first letter.
'yule' with its initial letter removed is 'ule'.
'jp' going around 'ule' is 'JULEP'.
(Other definitions for julep that I've seen before include "See 21 Down" , "Mint drink in America" , "Cocktail of bourbon, sugar and mint over crushed ice" , "(Minted) drink made with bourbon, sugar and crushed ice" , "Sweet drink, often medicated" .)