To Charles, a half of beer (6)
I believe the answer is:
chaser
'to charles a half of beer' is the definition.
I can't judge whether this definition defines the answer.
'charles a half of beer' is the wordplay.
'charles' becomes 'Chas' (shortened form).
'a half of' means to take half the letters.
'beer' with half the letters taken is 'er'.
'chas'+'er'='CHASER'
Can you help me to learn more?
(Other definitions for chaser that I've seen before include "Pursuit cannon; one engraving" , "Drink that follows immediately after another one" , "different drink to follow" , "Pursuer - of beer after whiskey?" , "Drink following one of another sort" .)