Being at home, possibly greet a number (7)
I believe the answer is:
integer
'a number' is the definition.
(integer is a kind of number)
'being at home possibly greet' is the wordplay.
'being at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'possibly' indicates an anagram.
'greet' anagrammed gives 'teger'.
'in'+'teger'='INTEGER'
(Other definitions for integer that I've seen before include "The whole thing" , "Treeing (anag.)" , "Perhaps 60,000" , "Whole unit" , "rational number remains" .)