For question it is clear that, the second and third letters, fourth and fifth letters, sixth and seventh letters of the word mutually interchange positions to form the code.
So
C ⇒ C
I ⇘ R
R ⇗ I
C ⇘ U
U ⇗ C
L ⇘ A
A ⇗ L
R ⇒ R
so the code for CIRCULAR is CRIUCALR
