Criminals - they're regularly found in toilets (7)
I believe the answer is:
looters
'criminals' is the definition.
(looter is a kind of criminal)
'they're regularly found in toilets' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'found in' is an insertion indicator.
'toilets' becomes 'loos' (loo is a kind of toilet**).
The alternate letters of 'theyre' are 'ter'.
'ter' inserted inside 'loos' is 'LOOTERS'.
(Other definitions for looters that I've seen before include "Pillagers, freebooters" , "Plunderers" , "They steal during riots" .)