Old-fashioned ideas, wanting installation of party line (6)
I believe the answer is:
cordon
'old-fashioned ideas wanting' is the definition.
I can't tell whether this definition defines the answer.
'installation of party line' is the wordplay.
'installation of' becomes 'corn' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'party' becomes 'do' (do can informally mean a party).
'line' means one lot of letters goes inside another.
'corn' placed around 'do' is 'CORDON'.
Can you help me to learn more?
(Other definitions for cordon that I've seen before include "Line of guard to prevent access" , "Line, of police say, to prevent passsage in and out" , "Ribbon" , "Circle of policemen" , "In cooking, . . . . . . bleu is excellent" .)