This person needs appointment -- one brought in to liaise (7)
I believe the answer is:
mediate
'liaise' is the definition.
('mediate' can be a synonym of 'liaise')
'this person needs appointment one brought in' is the wordplay.
'this person' becomes 'me' (I've seen this in other clues).
'needs' means one lot of letters go next to another.
'appointment' becomes 'date' ('date' can be a synonym of 'appointment').
'one' becomes 'i' (Roman numeral).
'brought in' indicates putting letters inside.
'date' placed around 'i' is 'diate'.
'me'+'diate'='MEDIATE'
'to' is the link.
(Other definitions for mediate that I've seen before include "Act as negotiator or peacemaker" , "Conciliate" , "To referee" , "try to resolve dispute" , "Intercede" .)