Escort's car phone broken (8)
I believe the answer is:
chaperon
'escort's' is the definition.
(chaperoning is a kind of escorting)
'car phone broken' is the wordplay.
'broken' indicates an anagram.
'car'+'phone'='carphone'
'carphone' anagrammed gives 'CHAPERON'.
(Other definitions for chaperon that I've seen before include "Person accompanying girl or younger group" , "Preach on about older woman supervisor" , "Attendant" , "Girl minder from Cape Horn" , "Preach on about older woman in charge of girl" .)