Large order for a beer (5)
I believe the answer is:
lager
'for a beer' is the definition.
(type of beer)
'large order' is the wordplay.
'order' is an anagram indicator.
'large' is an anagram of 'LAGER'.
(Other definitions for lager that I've seen before include "Type of beer" , "Continental beer" , "The drink could be regal" , "Effervescent beer" , "Bottom-fermented beer" .)