Beetle badly injured one on road (8)
I believe the answer is:
ladybird
'beetle' is the definition.
(ladybird beetle is a kind of beetle)
'badly injured one on road' is the wordplay.
'injured' is an anagram indicator.
'one' becomes 'i' (Roman numeral).
'on' says to put letters next to each other.
'road' becomes 'rd' (abbreviation).
'badly' anagrammed gives 'ladyb'.
'ladyb'+'i'+'rd'='LADYBIRD'
(Other definitions for ladybird that I've seen before include "Red spotted beetle" , "Garden beetle" , "that's spotted in gardens" , "old children's book" , "spotted one that flies" .)