Stop ritual admitting clairvoyance (7)
I believe the answer is:
respite
'stop' is the definition.
(thesaurus)
'ritual admitting clairvoyance' is the wordplay.
'ritual' becomes 'rite' ('rite' can be a synonym of 'ritual').
'admitting' means one lot of letters goes inside another.
'clairvoyance' becomes 'esp' ('esp' can be a synonym of 'clairvoyance').
'rite' going around 'esp' is 'RESPITE'.
(Other definitions for respite that I've seen before include "temporary delay" , "Relief; breather" , "A lull" , "Abatement, rest" , "Pause; reprieve" .)