Arena made from soft metal? Thanks for nothing (7)

I believe the answer is:
stadium
'arena' is the definition.
(synonyms)
'soft metal? thanks for nothing' is the wordplay.
I cannot really see how this works, but
'metal?' could be 'ta' (Ta is an example) and 'ta' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'made from' acts as a link.
Can you help me to learn more?
(Other definitions for stadium that I've seen before include "Open-air sports venue" , "A major sports ground" , "Admit us (anag) - sports ground" , "Venue for sporting events, concerts etc" , "eg Yankee, Wembley" .)
