HARP ON is a phrase that means to persistently talk about something or to keep bringing up a topic. The crossword solutions for this phrase are BELABOR (7 letters), DWELL (5 letters), NAG (3 letters), RUBIN (5 letters), and ITERATE (7 letters). BELABOR means to discuss something at length, DWELL means to linger on a topic, NAG means to constantly criticize or complain, RUBIN is a type of harp, and ITERATE means to repeat something. All of these words can be used to describe the phrase HARP ON.