Reptile injured a printer (8)
I believe the answer is:
terrapin
'reptile' is the definition.
(terrapin is a kind of reptile)
'injured a printer' is the wordplay.
'injured' is an anagram indicator.
'a'+'printer'='aprinter'
'aprinter' is an anagram of 'TERRAPIN'.
(Other definitions for terrapin that I've seen before include "temporary building" , "Small species of turtle" , "Partner I found for freshwater tortoise" , "Web-footed turtle" , "Little turtle" .)