Bar hosting bash and bachelor party (8)
I believe the answer is:
clambake
'party' is the definition.
(I've seen this before)
'bar hosting bash and bachelor' is the wordplay.
'bar' becomes 'cake' (synonyms).
'hosting' indicates putting letters inside (inserted letters are welcomed in or hosted).
'bash' becomes 'lam' (both can mean to hit).
'and' is a charade indicator (letters next to each other).
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'lam'+'b'='lamb'
'cake' going around 'lamb' is 'CLAMBAKE'.
(Other definitions for clambake that I've seen before include "Picnic, American style" , "eating by the sea" , "Outdoor gathering to eat seafood (US)" , "Picnic in America" , "Picnic over the pond" .)