Call to say the arena has been erected (4,2)
I believe the answer is:
ring up
'call' is the definition.
(I've seen this in another clue)
'the arena has been erected' is the wordplay.
I cannot quite see how this works, but
'arena' could be 'ring' (I've seen this in other clues) and 'ring' is found in the answer.
'erected' could be 'up' and 'up' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'to say' acts as a link.
Can you help me to learn more?
(Other definitions for ring up that I've seen before include "Telephone someone or record on cash register" , "Contact by phone" , "Try to contact" .)