The term 'well up' can be solved by the crossword solutions of 'TEAR' (4 letters) and 'SURGE' (5 letters). 'Well up' is an idiom that means to become filled with emotion, usually tears, or to suddenly increase in intensity. It is often used to describe a feeling of sadness or joy that is so strong that it cannot be contained. 'TEAR' is a noun that refers to a drop of salty liquid that comes from the eyes when someone is crying. 'SURGE' is a verb that means to rise suddenly and powerfully, like a wave.