Fuss around an essential component of life for a fighter (7)
I believe the answer is:
tornado
'a fighter' is the definition.
(tornado can mean a violent person)
'fuss around an essential component of life' is the wordplay.
'fuss' becomes 'todo' (I've seen this before).
'around' is an insertion indicator.
'an essential component of life' becomes 'rna' (abbreviation for ribonucleic acid).
'todo' going around 'rna' is 'TORNADO'.
'for' acts as a link.
(Other definitions for tornado that I've seen before include "A violent and destructive whirlwind" , "Destructive windstorm" , "Violent twister" , "Destructive weather" , "Destructive wind vortex" .)