Lying about top arrest (9)
I believe the answer is:
prostrate
'lying' is the definition.
(I've seen this before)
'about top arrest' is the wordplay.
'about' indicates anagramming the letters.
'top'+'arrest'='toparrest'
'toparrest' with letters rearranged gives 'PROSTRATE'.
(Other definitions for prostrate that I've seen before include "Lying face downwards" , "Flat" , "no longer able to stand" , "helpless" , "Totally exhausted" .)