Witchcraft would inevitably cause concern among chiefs (5)
I believe the answer is:
wicca
'witchcraft' is the definition.
(I've seen this before)
'would inevitably cause concern among chiefs' is the wordplay.
'chiefs' says to take the initial letters.
The first letters of 'would inevitably cause concern among' is 'WICCA'.
(Other definitions for wicca that I've seen before include "paganism" , "Practice of witchcraft" , "Cult of modern witchcraft" , "Magic" .)