Unknown fate when swallowing drug with a fanatic (6)
I believe the answer is:
Here is my best explanation:
'fanatic' is the definition.
(I've seen this before)
'unknown fate when swallowing drug with a' is the wordplay.
'unknown' becomes 'z' (algebra).
'fate' becomes 'lot' (synonyms).
'when swallowing' is an insertion indicator.
'drug' becomes 'e' (e is another name for ecstasy).
'with' indicates putting letters inside.
'zlot' placed around 'e' is 'zelot'.
'zelot' going around 'a' is 'ZEALOT'.