Coroner initially gets a bad scare on seeing dead body (7)
I believe the answer is:
carcase
'dead body' is the definition.
(carcase is a kind of dead body)
'coroner initially gets a bad scare on' is the wordplay.
'initially' suggests taking the first letters.
'gets' says to put letters next to each other.
'bad' is an anagram indicator.
'on' means one lot of letters goes inside another (as in clothing \'on\' a person).
The initial letter of 'coroner' is 'c'.
'scare' is an anagram of 'rcase'.
'a' placed into 'rcase' is 'arcase'.
'c'+'arcase'='CARCASE'
'seeing' acts as a link.
(Other definitions for carcase that I've seen before include "Corpse" , "Have his - (D L Sayers)" , "remains" , "Body of dead meat" , "Dead body of an animal" .)