Be with duelling Joe performing for anniversary (6,7)
I believe the answer is:
golden jubilee
'for anniversary' is the definition.
(I have seen 'Fiftieth anniversary ' mean 'golden jubilee' so perhaps 'anniversary' could also mean 'golden jubilee')
'be with duelling joe performing' is the wordplay.
'with' is a charade indicator (letters next to each other).
'performing' indicates anagramming the letters (the letters move around or 'perform').
'be'+'duelling'+'joe'='beduellingjoe'
'beduellingjoe' anagrammed gives 'GOLDEN JUBILEE'.
(Other definitions for golden jubilee that I've seen before include "Fiftieth anniversary of special event" , "A 50th anniversary" , "Celebration after 50 years" .)