Porn is circulating in jail (6)
I believe the answer is:
prison
'jail' is the definition.
(I know that jail can be written as prison)
'porn is circulating' is the wordplay.
'circulating' is an anagram indicator.
'porn'+'is'='pornis'
'pornis' anagrammed gives 'PRISON'.
'in' is the link.
(Other definitions for prison that I've seen before include "Slammer" , "Cooler" , "Clink - jug" , "Eg, Wormwood Scrubs" , "Stir - can" .)