Cryptic Clue

[Mysterons]

Professional detention centre containing internal security (6)

[Mampara]

Prison.....PRO (professional) I S (Internal security) N ( centre of deteNtion)

[turnerjmw]

Sounds right, Mampara. Could also conceivably be WISARD (an old spelling of wizard, which can mean expert), being IS (internal security) in WARD (place of detention). It would have to be Listeneresque to be that, though

[Aquagility]

Can't find Listeneresque in Chambers!

[turnerjmw]

Really? It's in my Special Edition 2009. Means "abstruse, obscure to the point of absurdity"

[Mysterons]

I've marked Mampara's answer as Best - top marks to turnerjmw for a feasible alternative, and a neologism !