Insert it about married arrangement (7)
I believe the answer is:
implant
'insert' is the definition.
(I know that implant has the is a more specific form of the action insert)
'it about married arrangement' is the wordplay.
'about' is an insertion indicator.
'married' becomes 'm' (abbreviation, e.g. in genealogy).
'arrangement' becomes 'plan' (plan is a kind of arrangement).
'm'+'plan'='mplan'
'it' placed around 'mplan' is 'IMPLANT'.
(Other definitions for implant that I've seen before include "Inculcate; embed" , "Bristol may get boost from this" , "New element in trap" , "Fix securely and deeply" , "Insert within a body" .)