Various fellows immersed in their work (6)
I believe the answer is:
divers
'various' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for divers that I've seen before include "Plungers" , "Several; frogmen" , "Way back, various" , "seabirds" , "Various; frogmen" .)