Rugby player hits low note, roughly a fortnightly occurrence (4-4)
I believe the answer is:
half-moon
'roughly a fortnightly occurrence' is the definition.
(a half-moon occurs roughly every fortnight)
'rugby player hits low note' is the wordplay.
'rugby player' becomes 'half' (short for half-back).
'hits' says to put letters next to each other (some letters hit or touch others).
'low' becomes 'moo' (lowing of cattle is their sound).
'note' becomes 'n' (abbreviation).
'half'+'moo'+'n'='HALF-MOON'
(Other definitions for half-moon that I've seen before include "Earth's satellite at first (or last) quarter" , "Semi-visible natural satellite" .)