Bloomer affected one performing (7)
I believe the answer is:
campion
'bloomer' is the definition.
(campion is a kind of flowering plant)
'affected one performing' is the wordplay.
'affected' becomes 'camp' (I've seen this before).
'one' becomes 'i' (Roman numeral).
'performing' becomes 'on' (I've seen this in other clues).
'camp'+'i'+'on'='CAMPION'
(Other definitions for campion that I've seen before include "Film director" , "Wild flower (red, white or bladder)" , "Here's one blooming" , "Plant with pink or white flowers" , "Edmund ---, martyr; Thomas ---, poet/lute composer" .)