This is a trick.
Prepend to the letter you want to search a strange string:
$letter = '§§§' . 'a'; // strange string plus the letter you want to search
Then apply a filter to terms_clauses
hook:
add_filter('terms_clauses', 'replace_name__like_for_ingredients', 10, 3);
$terms = get_terms( "ingredient", array( 'name__like' => $letter ) );
Finally use that function to remove the %
preceding the strange string and the strange string itself:
function replace_name__like_for_ingredient( $pieces, $taxonomies, $args ) {
if ( in_array('ingredient', $taxonomies) ) {
// replace the perc sign plus strange string with empty string so
// LIKE '%§§§a%' become LIKE 'a%'
$pieces['where'] = str_replace("%§§§", '', $pieces['where']);
}
return $pieces;
}
Untested.