The term 'ONE OF A DEADLY SEVEN' refers to the seven deadly sins, which are a set of vices that have been recognized since early Christian times. The two crossword solutions for this term are SIN (3 letters) and ENVY (4 letters). SIN is defined as an immoral act considered to be a transgression against divine law, while ENVY is defined as a feeling of discontent or resentment aroused by someone else's possessions, qualities, or luck. Together, these two words represent two of the seven deadly sins.