We often hear about supporting the note when singing.
This support comes with a contraction from the Pelvic floor.
It is an internal action, (women learn about Pelvic floor exercises in child birth) although it is important for all singers male and female to practice using this group of muscles and understand their importance when singing.

We pull up from the pelvic floor to support a note as we move higher through our vocal range.

This may not make much sense to a new singer, but it will become more apparent as we get to know our voice and how to utilise our facility (our body)

To understand how we pull up from the pelvic floor with out the confusing technical jargon if we imagine….

…There is a long piece of string with a large cork hanging from one end, the sting is threaded through the body from the groin and comes out at the top of your head, if someone were to gently pull the string from the top, you can imagine what would happen at the other end where the cork is… It will not pass through the body but this would create a lift from the pelvic floor area.
This is an internal action and we do not need to clench our buttocks but we do need to pull up through our body and use this support to make a connection with the voice.