Fling and booze-up, one admitted, is a bloomer (7)
I believe the answer is:
lobelia
'bloomer' is the definition.
(blooming flower)
'fling and booze-up one admitted' is the wordplay.
'fling' becomes 'lob' (both can mean to throw).
'and' is a charade indicator (letters next to each other).
'booze up' becomes 'ela' (I am not sure about this - if you are sure you should believe this answer much more).
'one' becomes 'i' (Roman numeral).
'admitted' indicates putting letters inside (inserted letters get admitted).
'ela' going around 'i' is 'elia'.
'lob'+'elia'='LOBELIA'
'is a' is the link.
Can you help me to learn more?
(Other definitions for lobelia that I've seen before include "Tropical or subtropical bedding plant" , "Showy garden flower" , "Garden plant with five-lobed flowers" , "Common garden plant; oil bale (anag.)" , "Lo, I bale out the flower" .)