Ancient characters around Omagh? (5)
I believe the answer is:
ogham
'ancient characters' is the definition.
(historical Irish alphabet)
'around omagh?' is the wordplay.
'around' indicates an anagram.
'omagh' is an anagram of 'OGHAM'.
(Other definitions for ogham that I've seen before include "Old Irish alphabet of carved lines and notches" , "Old Irish alphabet with letters of lines and notches" , "Old Irish alphabetical system with lines and notches in stone" , "Old Irish writing of carved lines and notches" , "Old Celtic alphabet" .)