crust 
/ˈkrʌst/ noun
plural crusts /ˈkrʌst/ noun 1 : the hard outer surface of bread [count] ▪ Her children prefer to eat their sandwiches with the crusts [=the outer edges of the bread slices] cut off. ▪ a crunchy/chewy crust [noncount] ▪ Her children prefer to eat their sandwiches with the crust cut off. 2 : the outside part of a pie : piecrust [count] ▪ Bake the pie until the crust [=top] is golden brown. [noncount] ▪ a pie with flaky crust 3 [count, noncount] : the bread that is used to make a pizza
▪ He likes pizza with thin/thick crust. ▪ She ate three slices of pizza, but left the crusts [=the thick, outer pieces of the crust] on her plate. 4 [count, noncount] : a hard layer on the surface of something
▪ Our feet broke through the thin crust of ice and into the snow below. ▪ the Earth's crust
▪ He likes pizza with thin/thick crust. ▪ She ate three slices of pizza, but left the crusts [=the thick, outer pieces of the crust] on her plate.
▪ Our feet broke through the thin crust of ice and into the snow below. ▪ the Earth's crust
earn a/your crust
Brit, informal : to earn the money that you need to live : to earn a living
▪ I'm really a poet, but I've got to earn my crust as an accountant.
▪ I'm really a poet, but I've got to earn my crust as an accountant.
— see also upper crust
