A greeting for everybody in the house (5)
I believe the answer is:
hallo
'a greeting' is the definition.
(alternative to hello)
'everybody in the house' is the wordplay.
'everybody' becomes 'all' (all people).
'in the' means one lot of letters goes inside another.
'house' becomes 'ho' (abbreviation for house).
'all' put inside 'ho' is 'HALLO'.
'for' is the link.
(Other definitions for hallo that I've seen before include "welcoming for visitors?" , "First indication" , "everyone in house" , "greeting" , "Word welcoming" .)