Prison entrance breached by careering tram (8)
I believe the answer is:
dartmoor
'prison' is the definition.
(English prison)
'entrance breached by careering tram' is the wordplay.
'entrance' becomes 'door' (door is a kind of entrance).
'breached by' is an insertion indicator (inserted letters break into or breach the word).
'careering' is an anagram indicator (careering can mean moving violently).
'tram' with letters rearranged gives 'artm'.
'door' placed around 'artm' is 'DARTMOOR'.
(Other definitions for dartmoor that I've seen before include "West Country prison" , "Upland region in Devon" , "National Park in Devon" , "Famous English prison in Devon" , "with ponies?" .)