Ruler over Laks is initially good, then roguish (8)
I believe the answer is:
oligarch
'ruler' is the definition.
(oligarch is a kind of ruler)
'over laks is initially good then roguish' is the wordplay.
'initially' says to take the initial letters.
'good' becomes 'g' (abbreviation).
'then' says to put letters next to each other.
'roguish' becomes 'arch' (I've seen this before**).
The first letters of 'over laks is' is 'oli'.
'oli'+'g'+'arch'='OLIGARCH'
(Other definitions for oligarch that I've seen before include "Member of small ruling group" , "Rich Russian with political influence" , "Mega-rich Russian with political influence" , "Member of ruling clique" , "Very rich Russian businessman" .)