LISP: A dynamic car

I have a complex list of lists and want something to check the second element of every list of the list in the loop, any supported features like this?

>>3
basically we have the following
(arch (parts lintel post1 post2)
    (lintel must-be-supported-by post1)
    (lintel must-be-supported-by post2)
    (lintel a-kind-of wedge)
    (post1 a-kind-of brick)
    (post1 must-not-touch post2)
    (post2 must-not-touch post1))
and must break it apart, personally I want to just use a buzzword checker and append them to the associated buzzword list

sorry if I'm not clear