WordPress at a glance
filter is not described

terms_clauses filter-hook . WP 3.1.0

Filters the terms query SQL clauses.

Usage

add_filter( 'terms_clauses', 'filter_function_name_4612', 10, 3 );
function filter_function_name_4612( $pieces, $taxonomies, $args ){
	// filter...

	return $pieces;
}
$pieces(string[])
Array of query SQL clauses.
$taxonomies(string[])
An array of taxonomy names.
$args(array)
An array of term query arguments.

Where the hook is called

WP_Term_Query::get_terms()
terms_clauses
wp-includes/class-wp-term-query.php 654
$clauses = apply_filters( 'terms_clauses', compact( 'fields', 'join', 'where', 'distinct', 'orderby', 'order', 'limits' ), $taxonomies, $args );

Where the hook is used (in WP core)

Does not used.