Shock old doctor, quietly, during call (9)
I believe the answer is:
bombshell
'shock' is the definition.
(bombshell can mean a great shock)
'old doctor quietly during call' is the wordplay.
'old doctor' becomes 'omb' (I can't justify this - if you can you should give a lot more credence to this answer).
'quietly' becomes 'sh' (both are used to tell someone to be quiet).
'during' is an insertion indicator.
'call' becomes 'bell' (bell can mean a phone call).
'omb'+'sh'='ombsh'
'ombsh' going into 'bell' is 'BOMBSHELL'.
Can you help me to learn more?
(Other definitions for bombshell that I've seen before include "attractive blonde" , "awful surprise" , "Unpleasant surprise" , "big disappointment" , "Overwhelming surprise" .)