At home and not at home, to some extent (2,1,3)
I believe the answer is:
in a way
'to some extent' is the definition.
(I've seen this before)
'at home and not at home' is the wordplay.
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'and' means one lot of letters go next to another.
'not at home' becomes 'away' (I've seen this before).
'in'+'away'='IN A WAY'
(Other definitions for in a way that I've seen before include "from one point of view" , "Sort of, to a limited extent" , "From some points of view" , "In some respects, to a limited extent" , "Sort of, in some respects" .)