Nurse translating letters (5)
I believe the answer is:
runes
'letters' is the definition.
(I know this)
'nurse translating' is the wordplay.
'translating' is an anagram indicator (I've seen 'translate' mean this).
'nurse' is an anagram of 'RUNES'.
(Other definitions for runes that I've seen before include "Old letters" , "Small stones bearing symbols with magic significance" , "Mysterious letters" , "marks on old tablets" , "old characters" .)