Carl Zeiss regularly drinks (4)
I believe the answer is:
ales
'drinks' is the definition.
(ale is a kind of drink)
'carl zeiss regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'carl'+'zeiss'='carlzeiss'
The alternating letters of 'carlzeiss' are 'ALES'.
(Other definitions for ales that I've seen before include "What might be delivered by pumps" , "Alcoholic drinks" , "Types of beer" , "A sale of beers" .)