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