Doctor scowled at sign of nervousness (4,5)
I believe the answer is:
cold sweat
'sign of nervousness' is the definition.
'cold sweat' can be an answer for 'nervousness' (thesaurus). I am not sure about the 'sign of' bit.
'doctor scowled at' is the wordplay.
'doctor' indicates an anagram.
'scowled' is an anagram of 'coldswe'.
'coldswe'+'at'='COLD SWEAT'
Can you help me to learn more?
(Other definitions for cold sweat that I've seen before include "nervous reaction" , "Symptom of fear" , "Symptom of nervousness or illness" , "Chilly perspiration brought on by fear" , "Chilled perspiration" .)