Your question assumes that people typically learn the kanji, for instance 歩, and then go on to try to figure out what extra meaning the okurigana impart on the kanji -- for instance, the addition of く creates a verb 歩く "to walk", and the addition of いた to 歩 creates the past tense verb "walked".
This is not the typical approach.
The typical approach is to learn the word あるく, and learn that it is written with the kanji 歩, and that the okurigana part is く (so it's not, say, 歩るく). And you know how to inflect the word into various tenses because of its type (く verb) and the grammar rules you've learned for that type of word.
Looking at all your questions, I get the impression that you view Japanese as a series of kanji (which each have many different on and kun readings that could potentially be used) with okurigana and particles mixed in.
Instead, you should view it as a series of words divided by particles, with some of the words being partially written using one or more kanji, and each word being read in usually just one way which is learned when you first see the word.
I've never heard of people teaching or learning "how to use okurigana" -- they learn "how to inflect verbs and adjectives", and the fact that the kana you use for this are called okurigana when they follow a kanji is incidental.
With regards to the example used in your original question, then, you are asking for the meaning of the word created when you add the character つ to 一. In that case, if you are unfamiliar with the word, you should look up in a dictionary (or probably a textbook since it's a simple word). You say "without specifically looking it up", but it is unnatural to expect a kanji resource to teach you the meaning of specific words.
The type of resource that lists kanji along with their readings and meanings is useful for the following tasks:
- I've never seen that kanji before. I wonder what words it's used in (that I can then look up and learn if I don't recognize them)?
- I wonder if this kanji is read in any ways that I'm not familiar with from the words I know, and how it's read in names? How might it be read in an unfamiliar compound that isn't listed, so I can look that compound up in a dictionary?
- I wonder what the common thread of meaning is between words that use this kanji? What is the "general meaning", "general sense" imparted by this kanji? (aids in understanding the etymology of words and keeping straight which kanji to use)
- Am I writing the right kanji or one that looks very similar? (check meaning/readings/compounds to see if they line up with what you expect)
- I wonder how the okurigana is broken up for this kanji? Was it o(konau), oko(nau) or okona(u)?
...things like that. Expecting the kanji dictionary to teach you the specific meaning of specific words is a bad idea.