Small possibility left about ghost materialising in new form (4,4)

I believe the answer is:
long shot
'small possibility' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'left about ghost materialising in new form' is the wordplay.
I cannot really see how this works, but
'left' could be 'l' (common abbreviation) and 'l' is located in the answer.
'about' could be 'on' (as in a book 'on' a certain topic) and 'on' is located in the answer.
an anagram of 'ghost' is 'gshot' which is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for long shot that I've seen before include "Something with slight chance of success" , "telephoto picture?" , "One has little chance of succeeding" , "Poor prospect" , "Something unlikely" .)
