Every so often plan to ruin cunning tribal leader (9)

I believe the answer is:

patriarch

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'tribal leader' is the definition.
'patriarch' can be an answer for 'leader' (patriarch is a kind of leader). I am unsure of the 'tribal' bit.

'every so often plan to ruin cunning' is the wordplay.
'every so often' means one should take alternating letters.
'cunning' becomes 'arch' (arch can mean cunning or tricksy).
'plan'+'to'+'ruin'='plantoruin'
The alternate letters of 'plantoruin' are 'patri'.
'patri'+'arch'='PATRIARCH'

Can you help me to learn more?

(Other definitions for patriarch that I've seen before include "Abraham or Isaac, perhaps" , "Father figure" , "tribal head" , "like Abraham was" , "Paterfamilias" .)

I've seen this clue in The Independent.

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