Silly laughter? A measure of gravity becomes British pilot (7)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

Silly laughter = GIGGLES, the G for gravity becomes B for British, giving us James Bigglesworth a.k.a. Biggles, hero of about 100 books by W.E. Johns, most of which I read avidly 70 or so years ago. “Let’s show those sausage guzzlers what this thing can do!”