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 give a lot more credence to this answer).
'to' means one lot of letters go next to another.
'out' means to remove the last letter.
'wrongly' is an anagram indicator.
'call' with its final letter removed is 'cal'.
'cal' anagrammed gives 'lac'.
'li'+'lac'='LILAC'
'is' acts as a 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" .)