Head of state is stock market malefactor? No way! (5)

I believe the answer is:

ruler

I'm a little stuck... Click here to teach me more about this clue!

'head of state' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for ruler that I've seen before include "One for drawing lines" , "Leader - line-drawing aid" , "Controller" , "One exercising control" , "King, president etc." .)

I've seen this clue in The Guardian.

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