While the weave functions as the "battery" which supplies the power for all magic, arcane and divine magic access that power differently. Arcane casters access magic by manipulating the structure of the weave itself, whether it be through direct connection (sorcerer), "performance" (bard), rigorous study (wizard), or backdoor hacking (warlock). Divines access their magic by being granted those abilities from their diety (cleric/ FvS/ Paladin) or from nature (druid / ranger). This is also one of the main reasons why divine magic tends to be less explody than arcane magic.
So to get back to the question you were responding to: How does being a cleric help you with casting arcane spells that your deity probably doesn't want you to have (else they would have put it in your class spell list)?