Glasgow football team (6)
I believe the answer is:
celtic
'glasgow football team' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for celtic that I've seen before include "Of a group of languages such as Gaelic and Welsh" , "Scottish football team" , "This tiger is credited with Irish prosperity" , "Relating to Irish, Gaelic, Manx, Welsh, etc" , "Racial of Welsh, Irish etc." .)