Thus, on half days, one gets a drink (4)
I believe the answer is:
soda
'a drink' is the definition.
(soda is a kind of drink)
'thus on half days one' is the wordplay.
'thus' becomes 'so' (synonyms).
'on' is a charade indicator (letters next to each other).
'half days' becomes 'd' (I am not sure about the 'half' bit.).
'one' becomes 'a'.
'so'+'d'+'a'='SODA'
'gets' is the link.
Can you help me to learn more?
(Other definitions for soda that I've seen before include "Drink containing carbonated water and sometimes flavouring" , ""Splashed" drinks mixer" , "Soft drink" , "Splash served with some spirits" , "Sodium carbonate" .)