18d.Mountaineer in charge of a group of climbers (5)
31aLower part of a shield; chief ingredient in a recipe; foundation in make-up; or, a military HQ (4)
32a.Equestrian kit and saddlery collectively; or, an alignment of a sailing boat to the wind (4)
36a.Group of divers collectively; or, a globule of gas in a liquid (6)
Guide
Base
Tack
Bubble