Coax, prevail upon (8)
I believe the answer is:
persuade
I believe this clue is a double definition.
'coax' is the first definition.
(I know this)
'prevail upon' is the second definition.
(I've seen this before)
(Other definitions for persuade that I've seen before include "'Coax, inveigle (8)'" , "Coax, prevail upon" , "Convince or induce, maybe coax" , "Talk round" , "Bring round" .)