Prediction favouring actors on Eastenders initially (8)
I believe the answer is:
forecast
'prediction' is the definition.
(forecast is a kind of prediction)
'favouring actors on eastenders initially' is the wordplay.
'favouring' becomes 'for' (I've seen this before).
'actors' becomes 'cast' (I've seen this before).
'on' means one lot of letters go next to another.
'initially' indicates taking the first letters.
The initial letter of 'eastenders' is 'e'.
'cast' after 'e' is 'ecast'.
'for'+'ecast'='FORECAST'
(Other definitions for forecast that I've seen before include "tip" , "Fear Scot in prediction" , "Expect" , "Prediction, about the weather perhaps" , "Predict (event)" .)