Gather as group of witches round start of night, end of June (7)
I believe the answer is:
convene
'gather' is the definition.
(convening is a kind of gathering)
'group of witches round start of night end of june' is the wordplay.
'group of witches' becomes 'coven' (I've seen this before).
'round' indicates putting letters inside.
'start of' says to take the initial letters.
'end of' suggests the final letters.
The initial letter of 'night' is 'n'.
The last letter of 'june' is 'e'.
'coven' going around 'n' is 'conven'.
'conven'+'e'='CONVENE'
'as' is the link.
(Other definitions for convene that I've seen before include "Muster" , "Call together" , "Assemble (for meeting)" , "rally" , "Gather (for meeting)" .)