As heads of state, they don't succeed (7)

I believe the answer is:

leaders

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

'as heads' is the definition.
'leaders' can be an answer for 'heads' (I've seen this in another clue). I am not certain of the 'as' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for leaders that I've seen before include "They take the initiative and direct others" , "Guides" , "newspaper articles" , "People to follow" , "Bosses" .)

I've seen this clue in the Evening Standard.

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