Tuck in

~ Literal meaning: To make someone comfortable in bed, especially a child, by arranging the covers around them.

                                   * E.g. When I was a child my dad used to tuck me in at bedtime.

~ Idiomatic meanig: To put the end of something such as a piece of clothing under or behind another piece in order to make it tidy.

                                   * E.g. You can wear this shirt loose or tucked in with a belt.