Accountant and graduate left small party (5)
I believe the answer is:
cabal
'small party' is the definition.
(I've seen this before)
'accountant and graduate left' is the wordplay.
'accountant' becomes 'ca' (abbreviation for chartered accountant).
'and' means one lot of letters go next to another.
'graduate' becomes 'ba'.
'left' becomes 'l' (common abbreviation).
'ca'+'ba'+'l'='CABAL'
(Other definitions for cabal that I've seen before include "Small group involved with intrigue" , "Camp" , "Intrigue, clique" , "Conspiring group" , "Secret plot; clique" .)