Tribal chief's brain specialist?

I believe the answer is:

headman

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'tribal chief's' is the definition.
(synonyms)

'brain specialist?' is the wordplay.
'brain' becomes 'head' (synonyms).
'specialist?' becomes 'man' (I can't justify this - if you can you should give a lot more credence to this answer).
'head'+'man'='HEADMAN'

Can you help me to learn more?

(Other definitions for headman that I've seen before include "Chieftain" , "Leader" , "Boss" , "Village chief" .)

I've seen this clue in The Daily Mail.

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