Cheap Shot, Punch When the Other Isn't Looking

This page is the CodyCross answer for the clue below from California, Group 1143, Puzzle 3 (Hollywood Walk of Fame).

Question is: Cheap Shot, Punch When the Other Isn't Looking

and the answer is: SUCKER

Word Meaning:

SUCKER — A person or animal that sucks, especially a breast or udder; especially a suckling animal, young mammal before it is weaned.

Definitions from Wiktionary.