Fighting idleness (8)
I believe the answer is:
inaction
'idleness' is the definition.
(thesaurus)
'fighting' is the wordplay.
I cannot quite understand how this works, but
'fighting' could be 'action' (as in military action) and 'action' is found within the answer.
The remaining letters 'in' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for inaction that I've seen before include "Idleness - fighting" , "Failure to exert oneself" , "Rest" , "Idleness of nicotian sort" , "Sluggishness" .)