He knows how to make bloomers! (5)
I believe the answer is:
baker
'he knows how to make bloomers' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he' is the wordplay.
I cannot quite understand how this works, but
'he' could be 'ker' and 'ker' is located in the answer.
The remaining letters 'ba' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for baker that I've seen before include "Producer of bread/cakes" , "Tradesman; Sherlock Holmes's Street" , "Loaf maker" , "His dozen is 13" , "Bread and cakes maker" .)