Intrude roughly to seize this person without warrant (9)
I believe the answer is:
unmerited
'without warrant' is the definition.
(unmerited can mean unwarranted or uncalled for)
'intrude roughly to seize this person' is the wordplay.
'roughly' indicates anagramming the letters.
'to seize' means one lot of letters goes inside another.
'this person' becomes 'me' (the person writing).
'intrude' with letters rearranged gives 'unrited'.
'unrited' placed around 'me' is 'UNMERITED'.
(Other definitions for unmerited that I've seen before include "Not earned" , "Not deserved" .)