Social occasion is routine after drink (3,5)
I believe the answer is:
tea party
'social' is the definition.
(I've seen this in another clue)
'occasion is routine after drink' is the wordplay.
I cannot quite see how this works, but
'occasion' could be 'party' (party is a kind of occasion) and 'party' is present in the answer.
'drink' could be 'tea' (tea is a drink) and 'tea' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tea party that I've seen before include "Social occasion (in Boston?)" , "Function 22 attended" , "US political movement" , "Staunch patriots" , "Function Alice attended" .)