Lead completely secures home game (7)
I believe the answer is:
pinball
'game' is the definition.
(pinball game is a kind of game)
'lead completely secures home' is the wordplay.
'lead' becomes 'pb' (Pb is the chemical symbol for lead).
'completely' becomes 'all' (synonyms).
'secures' means one lot of letters goes inside another.
'home' becomes 'in' ('he's home' can mean 'he's in').
'pb'+'all'='pball'
'pball' going around 'in' is 'PINBALL'.
(Other definitions for pinball that I've seen before include "Slot-machine game" , "It may require tilting when played" , "Electrically operated form of bagatelle" , "Slot machine bagatelle" , "Arcade game where a metal sphere negotiates hazards" .)