Telex VIP sent with ultimately vile obscenity (9)
I believe the answer is:
expletive
'obscenity' is the definition.
(thesaurus)
'telex vip sent with ultimately vile' is the wordplay.
'sent with' is an anagram indicator (send can mean to excite or stimulate).
'ultimately' suggests the final letters.
The last letter of 'vile' is 'e'.
'telex'+'vip'='telexvip'
'telexvip' anagrammed with 'e' can make 'EXPLETIVE'.
(Other definitions for expletive that I've seen before include "oath" , "Four-letter word" , "Dirty word" , "Swear word" , "Profane exclamation" .)