Played Seattle Seahawks and were disheartened and flat (9)
I believe the answer is:
'flat' is the definition.
(similar in meaning)
'played seattle seahawks and were disheartened' is the wordplay.
I cannot quite see how this works, but
an anagram of 'seattle' is 'tastele' which is within the answer.
This may be the basis of the clue (or it may be nonsense).
'and' is the link.
Can you help me to learn more?
(Other definitions for tasteless that I've seen before include "Lacking flavour or ability to appreciate the beautiful" , "Vapid" , "improper" , "Unseemly" , "Lacking flavour or aesthetic appreciation" .)