Trampled rodent running around middle of landing (7)
I believe the answer is:
trodden
'trampled' is the definition.
(I've seen this before)
'rodent running around middle of landing' is the wordplay.
'running' is an anagram indicator (the letters run around to different places).
'around' is an insertion indicator.
'middle of' means to look at the middle letters.
The middle of 'landing' is 'd'.
'rodent' is an anagram of 'troden'.
'troden' enclosing 'd' is 'TRODDEN'.
(Other definitions for trodden that I've seen before include "Oppressed" , "Footpaths are" , "Heavily walked upon" , "Crushed underfoot" , "Crushed under the feet" .)