They tweet seconds after upsetting football result? (7)
I believe the answer is:
linnets
'they tweet' is the definition.
(birds which tweet)
'seconds after upsetting football result?' is the wordplay.
'seconds' becomes 's'.
'after' means one lot of letters go next to another.
'upsetting' says the letters should be written in reverse.
'football result?' becomes 'ten nil' (10-0).
'tennil' in reverse letter order is 'linnet'.
's' after 'linnet' is 'LINNETS'.
(Other definitions for linnets that I've seen before include "Would they tweet" , "wingers" , "birds" , "Common finches" .)