Fight and fight again, nothing less (5)
I believe the answer is:
foray
'less' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'fight and fight again nothing' is the wordplay.
I cannot quite see how this works, but
'nothing' could be 'o' (O resembles 0) and 'o' is found within the answer.
'fight' could be 'fray' (fray is a kind of fight) and 'fray' is found in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for foray that I've seen before include "Depredation" , "Raid into enemy territory" , "Raid or incursion" , "Sortie" , "Brief incursion" .)