The term 'fill in' can refer to a variety of activities. The crossword solutions TELL (4 letters), INTERPOLATE (11 letters), CLUE (4 letters), WARN (4 letters), INK (3 letters), SUB (3 letters), TEMP (4 letters), DARKEN (6 letters), UPDATE (6 letters), APPRISE (7 letters), and STANDBY (7 letters) all relate to this term. To 'TELL' is to communicate information, while 'INTERPOLATE' is to insert something into a text or conversation. A 'CLUE' is a hint or suggestion that helps someone solve a problem or mystery. To 'WARN' is to alert someone to potential danger or risk. 'INK' is a dark liquid used for writing or printing. To 'SUB' is to substitute one thing for another. A 'TEMP' is a temporary worker. To 'DARKEN' is to make something darker in color or shade. To 'UPDATE' is to make something more current or modern. To 'APPRISE' is to inform someone of something. Finally, to 'STANDBY' is to be ready to act if needed.