p-cyanobenzoic acid is a nitrile group in the 1-position and a carboxylic acid group in the 4-position, these groups are para-substituted. However, both nitrile and carboxylic acid groups are electron-withdrawing, which means that they are both meta-directing groups when undergoing electrophilic substitution. At the same time, both groups are deactivating groups. Since they are both deactivating, it is possible that no further substitution will even occur.
For the sake of the question, we will assume that the reaction is allowed to take place. Therefore, each group will be trying to direct the to different meta-positions. The nitrile group is a much stronger withdrawing group, therefore, it will be the major directing group and the chloro will substitute in the position that is meta- to the nitrile, and ortho- to the carboxylic acid. The minor product would be the meta-position relative to the carboxylic acid. The reaction scheme provided shows the potential products of this reaction.