Hi,
This is a bit long-winded, but it's all I could think of.
With the data to be examined in A2:

=IF(MOD(LEN(A2),2)=1,IF(LEFT(A2,(LEN(A2)-1)/2)=RIGHT(A2,(LEN(A2)-1)/2),LEFT(A2,(LEN(A2)-1)/2),A2),A2)

Copy down as required.
Regards - Dave.