Spanish accent (5)
I believe the answer is:
tilde
'spanish accent' is the definition.
(accent mark written over n in Spanish)
This is the entire clue.
(Other definitions for tilde that I've seen before include "Sign on Spanish character" , "Significant mark" , "Spanish accent, as in se-or, ma-ana etc." , "senorita lacking one?" , "Spanish accent sign" .)