why is the truck not starting?

What is your question?

On 2007 Toyota Tacoma V6, 4x4, turn ignition switch on,and only hear a clicking sound, and dashboard lights go dim. Is the starter bad? The battery is fully charged. Engine not cranking over.

What makes this problem better or worse?

when ignition turned to on I hear clicking sound, and battery tends to drain, dashboard lights dim.

How long has your 2007 Toyota Tacoma had this problem?

just started.