Squib (3)
I believe the answer is:
dud
'squib' is the definition.
(I have seen 'Damp squib' mean 'dud' so perhaps 'squib' could also mean 'dud')
This is the entire clue.
(Other definitions for dud that I've seen before include "Failing to work properly" , "Just a palindromic flop" , "Something useless - a palindrome" , "Not functioning" , "Forged" .)