Have/take a gander (at something) verb phrase
If you have or take a gander at something, you look at something.
Take a gander at this mess! Clean it up at once!
Have a gander at her dress! How a beautiful one!
Come here and take a gander at this map!
To look at someone in an angry, contemptuous, or disapproving way
Meaning absolutely certain or without a doubt
I am as sure as God made little green apples that Peter's the one for you, you two make a beautiful couple.