The crossword solution for the term SUB (COVERTLY) is ROSA, which is a four-letter word. ROSA is a Spanish female name that is derived from the Latin word 'ROSA' meaning 'ROSE'. It is also used as a surname in some countries. In English, it is often used as an adjective to describe something that is done secretly or COVERTLY. Therefore, the term SUB (COVERTLY) can be interpreted as 'ROSA' and is used to describe something that is done in a clandestine manner.