A printer turning turtle (8)
I believe the answer is:
terrapin
'turtle' is the definition.
(terrapin is a kind of turtle)
'a printer turning' is the wordplay.
'turning' is an anagram indicator.
'a'+'printer'='aprinter'
'aprinter' is an anagram of 'TERRAPIN'.
(Other definitions for terrapin that I've seen before include "Small freshwater turtle" , "Chelonian reptile" , "Hardback" , "A reptile; a printer (anag.)" , "Little turtle" .)