Nurse translating letters (5)
I believe the answer is:
runes
'letters' is the definition.
(I have seen 'Old letters ' mean 'runes' so perhaps 'letters' could also mean 'runes')
'nurse translating' is the wordplay.
'translating' indicates anagramming the letters (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" .)