So, on Tuesday, he's apt to get drunk (3)
I believe the answer is:
sot
'drunk' is the definition.
(both can mean someone who drinks too much)
'so on tuesday' is the wordplay.
'on' means one lot of letters go next to another.
'tuesday' becomes 't'.
'so'+'t'='SOT'
'he's apt to get' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for sot that I've seen before include "Boozer" , "Habitual drinker" , "Habitual drunkard" , "Toper" , "A chronic drinker" .)