Sexual selection can favor the evolution of elaborate traits that natural selection acts against. How does sexual selection produce such extreme trait values in the face of opposing natural selection ?

The answer is: Linkage disequilibrium at alleles controlling the sexually selected trait and fitness bind them together evolutionarily.

Explanation:

Indirect selection can be said to operate at one locus resulting in genetic correlation with another locus, which is the main goal in the selection process. During the process of sexual choice, this commonly occurs when one preferred allele diffuses because it is out of balance with other alleles, which are benefited by natural selection or sexual selection.