We are able to take authority by virtue of our spiritual knowledge, though with humility and without ego. In dreams we will often find ourselves taking the lead before we are consciously able to do so.
Psychological / emotional perspective: Leadership qualities are not necessarily ones that everybody has or will use. Often we can surprise ourselves in dreams by doing things that we would not normally do, and becoming a leader is one of them.
Material aspects: Dreaming of a dog lead symbolizes the connection between ourselves and our lesser nature.
To have lost the dog lead would indicate a loss of control. Leading someone in a dream pre-supposes that we know what we are doing and where we are going. Being led suggests that we have allowed someone else to take control of a situation around us. You might also like to consult the entries for harness and halter.