I am old enough to remember watching "Billy Bunter " from Greyfriars on the TV (black and white on a small screen) and "Cave ! " was used a lot. There are probably some clips on youtube, but I haven't looked
One of the definitions of 'dressy' is 'indicating care in dressing', so it's maybe just one of those 'the whole clue defines it'? The'right gear' is meant to lead to us considering carss, driving. To me it's not a great clue!