Company holding a function in gambling venue (6)
I believe the answer is:
casino
'gambling venue' is the definition.
(I've seen this before)
'company holding a function' is the wordplay.
'company' becomes 'co' (abbreviation).
'holding' indicates putting letters inside.
'function' becomes 'sin' (mathematical function).
'a'+'sin'='asin'
'co' going around 'asin' is 'CASINO'.
'in' is the link.
(Other definitions for casino that I've seen before include "Gambling house" , "gambling joint" , "Where gambling may be seen" , "Gaming establishment" , "enterprise?" .)