Nothing beginning to scare old fighters (5)
I believe the answer is:
zeros
'old fighters' is the definition.
Although both the answer and definition are plural nouns, I can't see how they can define each other.
'nothing beginning to scare' is the wordplay.
'nothing' becomes 'zero' (synonyms).
'beginning to' says to take the initial letters.
The initial letter of 'scare' is 's'.
'zero'+'s'='ZEROS'
Can you help me to learn more?
(Other definitions for zeros that I've seen before include "zips" , "Noughts" , "loves" , "nothings" , "ducks" .)