What exactly is a Gentlemens cut? Is there a standard?
There's not really a gold standard.
It's typically a short side fading into a longer side/top. Scissor work on top, combed back or to either side.
The trend currently is an aggressively short side if not bald, fading up into scissor work on top, with a more defined part, combed back or to a side.
We had a conversation in here like a week ago about how popular pomade is nowadays.
If someone sat down and told me give them a gentlemen's and gave me no specifics, do what I want. I'd do a 1 on the side, fade up to a 3 1/2, scissor work on top, clipper over comb blend the sides/top, lightly define a part, and style it back and to the side with pomade and kick you out the door.