Current opposition that is limiting politician and party (9)

'current opposition' is the definition.
(resistance to electrical current)

'that is limiting politician and party' is the wordplay.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'limiting' means one lot of letters goes inside another.
'politician' becomes 'MP' (Member of Parliament).
'and' means one lot of letters go next to another.
'party' becomes 'dance' (dance is a kind of party).
'ie' placed around 'mp' is 'impe'.
'impe'+'dance'='IMPEDANCE'