... showing 3 attending a large hearing (5)
I believe the answer is:
trial
'hearing' is the definition.
(as in a court case)
'showing 3 attending a large' is the wordplay.
'showing i' becomes 'tri' (I can't explain this - if you can you should believe this answer much more).
'attending' means one lot of letters go next to another.
'large' becomes 'L' (eg in clothes sizes).
'tri'+'a'+'l'='TRIAL'
Can you help me to learn more?
(Other definitions for trial that I've seen before include "Test of ability" , "Legal hearing" , "show at Crufts?" , "Annoyance" , "Ordeal, perhaps in court" .)