It's not a puzzle you'll see very often, but certainly worth a look if you come across it. Seeing Double is a crossword in which each clue gives two separate definitions, resulting in two answers that differ by just one letter. The clue:
for example, would lead to the answers SLENDER and SLANDER. It is then up to the solver to discover which option fits with its neighbours in the grid.
The reason for the puzzle's scarcity is nothing to do with its appeal, and everything to do with its complexity for the setter. Finding suitable pairs of potential answers is only part of the problem. The changing letter must also fall on an intersected square in the grid if the puzzle is to have a unique solution.
The letter-change adds an element of wordplay to the puzzle's clue-solving and word-fitting, with some interesting pairs emerging. SAINTED might be TAINTED, or DREAMY become DREARY. All of which makes this apparently unassuming crossword a puzzle that word-lovers should really enjoy.
Each clue gives you two possible answers, which differ by just one letter. For example, the answers to one pair of clues could be MORSE and HORSE. The solver must decide which of the two answers should be used in each case to complete the grid.