Ultra vires unopened text message primarily scrapped (9)
I believe the answer is:
extremist
'ultra' is the definition.
(I know that ultra can be written as extremist)
'vires unopened text message primarily scrapped' is the wordplay.
'unopened' means to remove the first letter (without opening letter).
'primarily' indicates taking the first letters.
'scrapped' indicates an anagram.
The initial letter of 'message' is 'm'.
'vires' with its first letter taken off is 'ires'.
'ires'+'text'+'m'='irestextm'
'irestextm' with letters rearranged gives 'EXTREMIST'.
(Other definitions for extremist that I've seen before include "immoderate person" , "One with very radical views" , "One with highly non-standard views" , "Far left- or right-winger" , "outwardly fanatical" .)