Colossians 4:3
pray <4336> [praying.]
that <2443> [that.]
a door <2374> [a door.]
The term door is used metaphorically for an entrance to any business, or occasion or opportunity of doing any thing; and consequently "a door of utterance" is an opportunity of preaching the gospel successfully. See the parallel texts.
mystery <3466> [the mystery.]
for ...................... for <4012 1223> [for.]