What can be won at rugby? Nonsense written about Lomu's first cap (6,5)
I believe the answer is:
triple crown
'what can be won at rugby?' is the definition.
(won if one Home Nation defeats the other three)
'nonsense written about lomu's first cap' is the wordplay.
'nonsense' becomes 'tripe' (informal term for nonsense or false information).
'written about' indicates putting letters inside.
'lomu's first' becomes 'l' (1st letter of 'lomu').
'cap' becomes 'crown' (synonyms).
'tripe' placed around 'l' is 'triple'.
'triple'+'crown'='TRIPLE-CROWN'
(Other definitions for triple crown that I've seen before include "Victory over other three home nations" , "went to Ireland again this year [2007]" , "Headgear of Pope" .)