Clue: Sorcery making one snigger audibly? (5)
Answer: WICCA
Explanation: Definition: Sorcery
Homophone of "whicker" (meaning to snigger) – not of "wicker", as I initially tried in vain to justify. Anyone whose speech is Rhotic, or does not have the Whine-Wine Merger, might complain, but in the Slip for the recent Spoonerisms puzzle, Azed said "RP needs to be the norm throughout, I think."