Celtic's goalie dropping ball, running about (6)
I believe the answer is:
gaelic
'celtic's' is the definition.
(Gaelic is an example)
'goalie dropping ball running about' is the wordplay.
'dropping' suggests deleting specific letters.
'ball' becomes 'o' (O looks like a ball).
'running' indicates anagramming the letters (the letters run around to different places).
'about' becomes 'c' (abbreviation for circa).
'goalie' with 'o' taken away is 'galie'.
'galie' is an anagram of 'gaeli'.
'gaeli'+'c'='GAELIC'
(Other definitions for gaelic that I've seen before include "The native language of Ireland" , "Characteristic of the Celts" , "Speech" , "Irish language or Celtic language of Scotland" , "tongue" .)