The crossword solution for the term 'LESS DOUBTFUL' is 'SURER, ' which is a five-letter word. The term 'LESS DOUBTFUL' implies that something is more certain or reliable, and the word 'SURER' is an adjective that means having greater certainty or assurance. Therefore, the crossword solution of 'SURER' for the term 'LESS DOUBTFUL' is appropriate because it conveys the idea of greater certainty or reliability.