Cauldron primarily, cooker for witches (5)
I believe the answer is:
coven
'witches' is the definition.
(I've seen this in other clues)
'cauldron primarily cooker' is the wordplay.
'primarily' indicates taking the first letters.
'cooker' becomes 'oven' (I've seen this before**).
The initial letter of 'cauldron' is 'c'.
'c'+'oven'='COVEN'
'for' acts as a link.
(Other definitions for coven that I've seen before include "Group of witches" , "enchanting women in group" , "Company of witches" , "Some wise women" , "Witches' meeting" .)