Gun trained on head of unfortunately dead horse, perhaps (8)
I believe the answer is:
ungulate
'horse perhaps' is the definition.
(horse is a kind of ungulate)
'gun trained on head of unfortunately dead' is the wordplay.
'trained' is an anagram indicator (to train can mean to grow something into a shape).
'on' means one lot of letters goes inside another.
'head of' suggests taking the first letters.
'dead' becomes 'late' ('late' can be similar in meaning to 'dead'**).
The initial letter of 'unfortunately' is 'u'.
'gun' is an anagram of 'ngu'.
'u'+'late'='ulate'
'ngu' placed inside 'ulate' is 'UNGULATE'.
(Other definitions for ungulate that I've seen before include "Group of mammals having hooves" , "Hoofed animal" , "A gun lute was hoofed" , "Type of deer" , "Hoofed mammal" .)