For one to call out wrongly is a bloomer! (5)
I believe the answer is:
lilac
'a bloomer' is the definition.
(flowering plant)
'for one to call out wrongly' is the wordplay.
'for one' becomes 'li' (I can't justify this - if you can you should believe this answer much more).
'to' says to put letters next to each other.
'out' means to remove the last letter.
'wrongly' indicates anagramming the letters.
'call' with its final letter taken away is 'cal'.
'cal' anagrammed gives 'lac'.
'li'+'lac'='LILAC'
'is' is the link.
Can you help me to learn more?
(Other definitions for lilac that I've seen before include "garden ornamental" , "Shrub or small tree with fragrant blossom" , "Tree with pink blossoms" , "I call (anag)" , "Lavender-coloured" .)