Supposedly Arsenal's No.1 fumbled shot -- that's awful (2,6)
I believe the answer is:
as though
'supposedly arsenal's no' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'1 fumbled shot that's awful' is the wordplay.
I cannot really see how this works, but
'1' could be 'a' (both can mean one) and 'a' is found within the answer.
an anagram of 'shot' is 'stho' which is located in the answer.
'that's awful' could be 'ugh' (expression of disgust) and 'ugh' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for as though that I've seen is " Like".)