The East European twice used arena for sport (12)
I believe the answer is:
orienteering
'sport' is the definition.
Both the definition and answer are singular nouns.
Maybe there's a link between them I don't understand?
'the east european twice used arena' is the wordplay.
'the east' becomes 'orient' (synonyms).
'european' becomes 'E' (abbreviation e.g. EU).
'twice used' shows that letters should be duplicated.
'arena' becomes 'ring' (I've seen this in another clue).
'e' duplicated is 'ee'.
'orient'+'ee'+'ring'='ORIENTEERING'
'for' is the link.
Can you help me to learn more?
(Another definition for orienteering that I've seen is " Sport using map and compass".)