He's in a whirl (4)
I believe the answer is:
eddy
This clue is a double definition.
'he's' is the first definition.
'whirl' is the second definition.
(I know that whirl can be written as eddy)
'in a' acts as a link.
(Other definitions for eddy that I've seen before include "religious leader" , "Circle around" , "Whirlwind" , "Little swirl in water" , "Whirling current" .)