In cell, a malign priest (4)
I believe the answer is:
lama
'priest' is the definition.
(lama is a kind of priest)
'in cell a malign' is the wordplay.
'in' says the answer is hidden in the clue.
'LAMA' is hidden in the letters of 'cell a malign'.
(Other definitions for lama that I've seen before include "devout Buddhist" , "Religious leader" , "A Tibetan Buddhist priest or monk" , "A Buddhist priest in Tibet (4)" , "Tibetan spiritual leader" .)