Most advantageous silence over Epstein, oddly offed beforehand (7)
I believe the answer is:
optimum
'most advantageous' is the definition.
Both the answer and definition are adjectives. Maybe there's a link between them I don't understand?
'silence over epstein oddly offed beforehand' is the wordplay.
'silence' becomes 'mum' (as in 'mum's the word').
'over' says to put letters next to each other (in a down clue, some letters go over others).
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
'offed' becomes 'o' (this might be a standard abbreviation which I don't know about).
'beforehand' says to put letters next to each other.
The alternate letters of 'epstein' are 'pti'.
'pti' put after 'o' is 'opti'.
'mum' after 'opti' is 'OPTIMUM'.
Can you help me to learn more?
(Other definitions for optimum that I've seen before include "model" , "top condition" , "Best, most favourable" , "Most favourable amount" , "Most appropriate" .)