Whirling, it's pronouncedly less than steady (4)
I believe the answer is:
eddy
'steady' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for eddy that I've seen before include "current revolution" , "Rapid circular current" , "Founder of Christian Science, d. 1910" , "Little swirl in water" , "Chap" .)