Yes. Termites eat things that are made of wood and bars are typically made of wood. In this joke, tender means 'Does it taste good?'. But a bartender is someone who brings people drinks and things in a resturaunt that work behind the bar. So the termite is asking if the bar is tender, or good to eat.

Saisho no nōtobukku no entori

Watashi wa makkusudesu. Watashi ga yonde, utau no ga sukidesu. : )