Fish attending competition late in the day (8)
I believe the answer is:
eventide
'late in the day' is the definition.
(eventide means the evening)
'fish attending competition' is the wordplay.
'fish' becomes 'ide' (type of fish).
'attending' says to put letters next to each other (to attend can mean to follow).
'competition' becomes 'event' (sporting event).
'ide' after 'event' is 'EVENTIDE'.
(Other definitions for eventide that I've seen before include "some time later?" , "End of the day to the poet" , "End of the day (poetic)" , "when it starts to get dark" , "late in the day?" .)