Old Irish characters around Omagh (5)
I believe the answer is:
ogham
'old irish characters' is the definition.
'ogham' can be an answer for 'characters' (I have seen 'Old characters' mean 'ogham' so perhaps 'characters' could also mean 'ogham'). I am unsure of the 'old irish' bit.
'around omagh' is the wordplay.
'around' indicates an anagram.
'omagh' is an anagram of 'OGHAM'.
Can you help me to learn more?
(Other definitions for ogham that I've seen before include "Old Irish alphabetical system with lines and notches in stone" , "Celtic characters" , "set of characters" , "Old Irish writing system of lines and notches in stone" , "Old British characters" .)