Party time! Partying hard, bit woozy ultimately (8)
I believe the answer is:
birthday
'party time' is the definition.
(as in a birthday party)
'partying hard bit woozy ultimately' is the wordplay.
'partying' indicates anagramming the letters.
'ultimately' suggests the final letters.
The final letter of 'woozy' is 'y'.
'hard'+'bit'='hardbit'
'hardbit' anagrammed gives 'birthda'.
'birthda'+'y'='BIRTHDAY'
(Other definitions for birthday that I've seen before include "Arrival time" , "Natal anniversary" , "when one was delivered" , "annual event" , "It comes around once a year" .)