Upper-case letters (8)
I believe the answer is:
capitals
'upper-case letters' is the definition.
('capital' can be a synonym of 'upper-case letter')
This is the entire clue.
(Other definitions for capitals that I've seen before include "LETTERS LIKE THESE" , "Great cities or large letters" , "Upper-case letters" , "E.g. PARIS, ROME" , "First letters and first cities" .)