School holds function with drink (6)
I believe the answer is:
scotch
'drink' is the definition.
(Scotch is an example)
'school holds function' is the wordplay.
'school' becomes 'sch' (abbreviation).
'holds' means one lot of letters goes inside another.
'function' becomes 'cot' (short for cotagent, a mathematical function).
'sch' going around 'cot' is 'SCOTCH'.
'with' is the link.
(Other definitions for scotch that I've seen before include "Alcoholic spirit" , "Frustrate; quash" , "providing nursery facility in school" , "Northern whisky" , "Type of egg" .)