Bit of a bloomer letting it slip out (6)
I believe the answer is:
pistil
'bit of a bloomer letting' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'it slip out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'it'+'slip'='itslip'
'itslip' anagrammed gives 'PISTIL'.
Can you help me to learn more?
(Other definitions for pistil that I've seen before include "Female part of a plant" , "This part of a flower sounds like a gun" , "Style in flower" , "Seed-producing part of a flower" , "Stigma, style and ovary" .)