Attending in lieu of, to mollify (7)
I believe the answer is:
placate
'to mollify' is the definition.
('placate' can be a synonym of 'mollify')
'attending in lieu' is the wordplay.
'attending' becomes 'at' (I've seen this in other clues).
'in' means one lot of letters goes inside another.
'lieu' becomes 'place' ('place' can be a synonym of 'lieu').
'at' put inside 'place' is 'PLACATE'.
'of' is the link.
(Other definitions for placate that I've seen before include "Make calm, conciliate" , "Pale cat could pacify" , "Make less angry" , "Mollify, soothe anger" , "Mollify, calm down" .)