The molecule is a monosubstituted benzene. Number the ring so C1 carries the only substituent.

1. At C1: the ring carbon is bonded to an ester oxygen, which in turn is bonded to a carbonyl carbon (C1-O-C(=O)-).

2. From that carbonyl, a straight, saturated chain of exactly twenty-six methylene units extends (-(CH2)26-).

3. The chain terminates in a carboxylic acid (-C(=O)OH).

Summary of the substituent: -O-C(=O)-(CH2)26-C(=O)OH.