Idiot contributing to never-ending battle (7)
I believe the answer is:
dingbat
'idiot' is the definition.
(I've seen this before)
'contributing to never-ending battle' is the wordplay.
'contributing to' says the answer is hidden in the clue (the answer contributes to part of the clue ).
'DINGBAT' can be found hidden inside 'never ending battle'.
(Other definitions for dingbat that I've seen before include "Silly billy - it'd bang (anag)" , "Thingummy - bind tag (anag)" , "Simpleton" , "funny-looking character" , "plonker" .)