Sony mobile carried by highly-strung chauffeur who's always interfering (4,6)
I believe the answer is:
nosy parker
'chauffeur who's always interfering' is the definition.
I can't tell whether this definition defines the answer.
'sony mobile carried by highly-strung' is the wordplay.
'mobile' indicates an anagram (mobile can mean moving).
'carried by' is a charade indicator (letters next to each other) (in a down clue, some letters hold up others).
'highly strung' becomes 'parker' (I can't explain this - if you can you should give a lot more credence to this answer).
'sony' is an anagram of 'nosy'.
'nosy'+'parker'='NOSY-PARKER'
Can you help me to learn more?
(Other definitions for nosy parker that I've seen before include "Prying person" , "Interested party" , "busybody" , "snoop" .)