Trash in cities I tidied up, cleaner on the outskirts earlier (9)
I believe the answer is:
criticise
'trash' is the definition.
(I know that trash is a more specific form of the action belittle)
'cities i tidied up cleaner on the outskirts earlier' is the wordplay.
'tidied up' indicates anagramming the letters.
'on the outskirts' suggests removing the centre (letters at the outskirts of the word).
'earlier' means one lot of letters go next to another.
'cleaner' with its middle taken out is 'cr'.
'cities'+'i'='citiesi'
'citiesi' with letters rearranged gives 'iticise'.
'iticise' after 'cr' is 'CRITICISE'.
'in' is the link.
(Other definitions for criticise that I've seen before include "Point out problems or mistakes" , "knock" , "Find fault" .)