He's in a whirl (4)
I believe the answer is:
eddy
I believe this clue is a double definition.
'he's' is the first definition.
'a whirl' is the second definition.
(I've seen this before)
'in' 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" .)