Tardis regularly placed in street for convenience (7)
I believe the answer is:
latrine
'for convenience' is the definition.
(latrine is a kind of convenience)
'tardis regularly placed in street' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'placed in' is an insertion indicator (I've seen this in other clues).
'street' becomes 'lane'.
The alternate letters of 'tardis' are 'tri'.
'tri' inserted within 'lane' is 'LATRINE'.
(Other definitions for latrine that I've seen before include "A military lavatory" , "Camp lavatory" , "Lavatory (in barracks)" , "where to go in the army" , "Camp toilet" .)