Family company in GB meeting artist, a slithery creature (4,5)
I believe the answer is:
king cobra
'a slithery creature' is the definition.
'family company in gb meeting artist' is the wordplay.
'family' becomes 'kin' ('kin' can be a synonym of 'family'**).
'company' becomes 'co' (abbreviation).
'in' indicates putting letters inside.
'meeting' means one lot of letters go next to another.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'co' going into 'gb' is 'gcob'.
'kin'+'gcob'+'ra'='KING COBRA'
(Other definitions for king cobra that I've seen before include "hooded killer" , "Venomous type" , "venomous customer" , "Large Asiatic snake" , "enormous snake" .)