Deterioration rising, no one angry (7)
I believe the answer is:
erosion
'deterioration' is the definition.
'rising no one angry' is the wordplay.
'rising' says the letters should be written backwards (going up in a down clue).
'one' becomes 'i' (Roman numeral).
'angry' becomes 'sore' (similar in meaning).
'no'+'i'+'sore'='noisore'
'noisore' in reverse letter order is 'EROSION'.
(Other definitions for erosion that I've seen before include "being eaten away" , "Wearing away (of soil, rocks etc)" , "The wearing away by water or weather" , "Abrasion" , "Process of wear" .)