Part of flower set man off (6)
I believe the answer is:
stamen
'part of flower' is the definition.
(I know that bloom is a is part of of stamen)
'set man off' is the wordplay.
'off' is an anagram indicator.
'set'+'man'='setman'
'setman' with letters rearranged gives 'STAMEN'.
(Other definitions for stamen that I've seen before include "Manet's (anag.)" , "Fertiliser" , "Male reproductive organ of a flower" , "Part of a flowering plant" , "Male fertilising organ of flowering plants" .)