Annoy one rattier drunk (8)
I believe the answer is:
irritate
'annoy' is the definition.
(I know that annoy can be written as irritate)
'one rattier drunk' is the wordplay.
'one' becomes 'i' (Roman numeral).
'drunk' indicates anagramming the letters.
'rattier' is an anagram of 'rritate'.
'i'+'rritate'='IRRITATE'
(Other definitions for irritate that I've seen before include "Nettle and annoy" , "bug" , "badger" , "Wind up" , "Vex, aggravate" .)