Telegraph characters sent over in Times Roman (5)
I believe the answer is:
morse
'telegraph characters' is the definition.
(Morse code, letters sent by telegraph)
'sent over in times roman' is the wordplay.
'sent over' says the letters should be written backwards.
'in' says the answer is hidden in the clue.
'esrom' is hidden in the letters of 'times roman'.
'esrom' backwards is 'MORSE'.
(Other definitions for morse that I've seen before include "Endeavour" , "TV inspector" , "Colin Dexter's fictional detective" , "& 24 Across Encrypted language" , "Code; TV detective" .)