Fit most of the promos in a shiny metal container of genes (10)
I believe the answer is:
chromosome
'fit most of the promos' is the definition.
I can't tell whether this defines the answer.
'in a shiny metal container of genes' is the wordplay.
'in' indicates putting letters inside.
'a shiny metal' becomes 'chrome' (I've seen this before).
'container of genes' becomes 'omos' (I can't justify this - if you can you should give a lot more credence to this answer).
'chrome' going around 'omos' is 'CHROMOSOME'.
Can you help me to learn more?
(Other definitions for chromosome that I've seen before include "Genetic structure" , "Gene carrier" , "structure in cell" , "Structure carrying genes" , "this could be X or Y" .)