Not dead - having a beer about four! (5)
I believe the answer is:
alive
'not dead' is the definition.
('alive' is the opposite to 'dead')
'a beer about four' is the wordplay.
'a beer' becomes 'ale' (type of beer).
'about' indicates putting letters inside.
'four' becomes 'IV' (Roman numerals).
'ale' going around 'iv' is 'ALIVE'.
'having' is the link.
(Other definitions for alive that I've seen before include "Active - living" , "Existent" , "Extant" , "Go or walk briskly" , "operative?" .)