Printer's error in party politics (4)
I believe the answer is:
typo
'printer's error' is the definition.
(I've seen this before)
'in party politics' is the wordplay.
'in' says the answer is hidden in the clue.
'TYPO' is hidden in the letters of 'party politics'.
(Other definitions for typo that I've seen before include "Keyboard slip-up" , "Small keyboarding error" , "Literal - printing mistake" , "Printing error (colloq.)" , "Printer's error" .)