Staves off hail with periodic rites (6)
I believe the answer is:
averts
'staves off' is the definition.
('avert' can be a synonym of 'stave off')
'hail with periodic rites' is the wordplay.
'hail' becomes 'ave' (greeting in Latin).
'with' is a charade indicator (letters next to each other).
'periodic' indicates alternate letters (letters periodically taken).
The alternating letters of 'rites' are 'rts'.
'ave'+'rts'='AVERTS'
(Other definitions for averts that I've seen before include "Turns away or causes to turn away" , "Turns aside" , "Heads off, prevents from happening" , "Of eyes or gaze, turns away" , "Deflects, heads off" .)