Solution for 5 August cryptic crossword clue

One identifies bishop and rock pocketed by child (5)
Solution – mitre


So the first thing you need to know to be able to solve this clue is that a "mitre" is a funny sort of hat bishops wear.

The second part of the clue is of the container type.  That is "r" standing for "rock" is contained within "or pocketed by " a word which means child.  In this case "mite".  As in "the poor wee mite".  Mite does have other meanings of course – including the little insects.