Piece of fruit — round, as it happens (5)
I believe the answer is:
olive
'piece of fruit' is the definition.
'olive' can be an answer for 'fruit' (I've seen this in another clue). I am not certain of the 'piece of' bit.
'round as it happens' is the wordplay.
'round' becomes 'o' (o is a circular letter).
'as it happens' becomes 'live' (as in live television).
'o'+'live'='OLIVE'
Can you help me to learn more?
(Other definitions for olive that I've seen before include "Evergreen Mediterranean tree" , "Oil producer" , "Its branch is a peace emblem" , "Girl's name; tree" , "Greyish-green; fruit" .)