Particular person in prison will be visited by US lawyer (6)
I believe the answer is:
pedant
'particular person' is the definition.
(a pedantic or particular person)
'in prison will be visited by us lawyer' is the wordplay.
'in prison' becomes 'pent' ('pent' can mean 'confined').
'will be visited by' is an insertion indicator.
'us lawyer' becomes 'DA' (abbreviation for District Attorney).
'pent' going around 'da' is 'PEDANT'.
(Other definitions for pedant that I've seen before include "Old teacher" , "Panted (anag.)" , "Unimaginative person who insists on petty rules" , "Academically fussy person" , "Nitpicker" .)