Clue: Name the early Muslim leaders interrupting Christian child out of familiarity (8)
Answer: CONTEMPT
Explanation: Definition: child out of familiarity
Here is a turn-up for the books: the wordplay is clear – an envelope ('interrupting') of NTEM ('**N**ame **T**he **E**arly **M**uslim leaders') in COPT ('Christian') – but the difficulty is the definition. It is a reference to the saw "familiarity breeds contempt".