MP right at home in it makes impression (7)
I believe the answer is:
imprint
'impression' is the definition.
(I know that impression can be written as imprint)
'mp right at home in it' is the wordplay.
'right' becomes 'r' (common abbreviation).
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'in' is an insertion indicator.
'mp'+'r'+'in'='mprin'
'mprin' going within 'it' is 'IMPRINT'.
'makes' is the link.
(Other definitions for imprint that I've seen before include "Publisher's name; stamp" , "Mark made by pressing or stamping surface" , "make an impact" , "Mark produced by pressure" , "Stamp (with sense of identity)" .)