It's used to fence bounds of estate hosting games (4)
I believe the answer is:
epee
'it's used to fence' is the definition.
(blade used in fencing)
'bounds of estate hosting games' is the wordplay.
'bounds of' means to remove the middle letters (the letters which form the boundaries of the word).
'hosting' means one lot of letters goes inside another.
'games' becomes 'pe' (abbreviation for Physical Education).
'estate' with its middle taken out is 'ee'.
'ee' placed around 'pe' is 'EPEE'.
(Other definitions for epee that I've seen before include "Olympic event" , "Another fencing sword" , "Duelling blade" , "Type of sword" , "Thin fencing sword" .)