Bullet missing one from erratic shot (6)
I believe the answer is:
tracer
'bullet' is the definition.
(I've seen this before)
'one from erratic shot' is the wordplay.
'one' becomes 'i' (Roman numeral).
'from' indicates named letters should be taken away.
'shot' indicates anagramming the letters.
'erratic' with 'i' taken away is 'erratc'.
'erratc' anagrammed gives 'TRACER'.
'missing' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tracer that I've seen before include "Kind of bullet that leaves trail" , "This bullet leaves smoke in its passage" , "He's managed to find" , "ammunition" , "Bullet whose track can be seen - element tracking radiation" .)