The term 'clunker of a car' is used to describe an old, unreliable, and often dilapidated vehicle. The two crossword solutions for this term are HEAP and LEMON. HEAP is a four-letter word that means a large pile or mass, usually of something discarded or neglected. LEMON is a five-letter word that is used to describe a car that is defective or unsatisfactory in some way. Therefore, the two crossword solutions for the term 'clunker of a car' are HEAP and LEMON, which both refer to an old, unreliable, and often dilapidated vehicle.