Tea service one knocked over (5)
I believe the answer is:
Here is my best explanation:
'tea' is the definition.
(I've seen this before)
'service one knocked over' is the subsidiary indication.
'service' becomes 'mass' (I've seen this in other clues).
'one' becomes 'a'.
'knocked over' says the letters should be written backwards.
'massa' written backwards gives 'assam'.
(Other definitions for assam that I've seen before include "NE Indian state (tea)", "Type of tea", "Kind of Indian tea", "Tea-producing region", "Tea-growing state in north-east India", "Indian state known for its tea production", "Indian tea-growing state", "Indian state famous for tea", "Tea-growing Indian state" and "North-east Indian tea state".)