Peter to install something reliable for party (4,4)
I believe the answer is:
safe seat
'something reliable for party' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'peter to install' is the wordplay.
'peter' becomes 'safe' (slang term).
'to install' becomes 'seat' (seating is a kind of installing).
'safe'+'seat'='SAFE SEAT'
Can you help me to learn more?
(Other definitions for safe seat that I've seen before include "Politician's dream" , "Parliamentary constituency with a substantial majority for the incumbent" , "Constituency MP prefers" , "What politician would like" , "one of a great majority" .)