Large order of drink (5)
I believe the answer is:
lager
'drink' is the definition.
(lager is a kind of drink)
'large order' is the wordplay.
'order' indicates an anagram.
'large' anagrammed gives 'LAGER'.
'of' acts as a link.
(Other definitions for lager that I've seen before include "Effervescent beer" , "light ale" , "Regal sort of beer" , "Drink - 5 down (anag)" , "A brew" .)