At home, then 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 then not at home' is the wordplay.
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'then' is a charade indicator (letters next to each other).
'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 "Sort of, in some respects" , "Kind of" , "somehow" , "From some points of view" , "as one might see it" .)