Single desperado revealed that they had a gun, taking a chance on getting some money from this (3-5,6)
I believe the answer is:
one-armed bandit
'single' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'desperado revealed that they had a gun taking a chance on getting some money from this' is the wordplay.
I cannot quite see how this works, but
'desperado' could be 'bandit' (I've seen this before) and 'bandit' is found within the answer.
'had' could be 'd' (in contractions e.g. 'I'd', 'you'd' etc) and 'd' is present in the answer.
'a' could be 'one' and 'one' is found within the answer.
'gun' could be 'arm' (I've seen this in other clues) and 'arm' is found in the answer.
'from' could be 'e' (I've seen this in other clues) and 'e' is found 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 one-armed bandit that I've seen before include "Bend" , "Gambling machine" .)