Cajolery frequently succeeded in ongoing saga (4,4)
I believe the answer is:
soft soap
'cajolery' is the definition.
(soft soap is a kind of cajolery)
'frequently succeeded in ongoing saga' is the wordplay.
'frequently' becomes 'oft' (I've seen this before).
'succeeded' becomes 's' (genealogical abbreviation).
'in' means one lot of letters goes inside another.
'ongoing saga' becomes 'soap' (TV soap opera).
'oft'+'s'='ofts'
'ofts' going into 'soap' is 'SOFT-SOAP'.
(Other definitions for soft soap that I've seen before include "Use persuasive flattery" , "Use flattery to persuade" , "Flattery of cleansing sort?" , "(Use) flattering talk" , "Use flattery on (someone)" .)