My initial thought is
yellow or yellow billiard ball
but I can't make all the clues work.
Solid round the number 1,
The #1 billiard ball is a solid yellow, and "solid" is a term from billiards.
This clue may also indicate wordplay (a synonym of "solid" around the letter 'i'), or refer to some game where a "solid round" would be a score of 1 (for instance, golf).
A motley few, this road, walked on,
Assorted billiard balls roll around the table.
Yes I'm a coward now be gone,
"Yellow-belly" is a synonym of "coward".
Made of two but I am one!
There are actually two yellow billiard balls: a solid and a striped.
Submersing ship with unhinged crew,
Not sure about this one.
Twixt 'Of' and 'Gave' another clue,
Not sure about this one, but there is probably an idiom or phrasal verb having the form "gave __ of". For instance, "gave evidence of".
Never in a shade of blue,
Not sure about this one.
I warn of danger, please don't sue!
Yellow often symbolizes danger (think traffic lights or yield signs).