Doctor scowled at sign of fear (4,5)
I believe the answer is:
cold sweat
'sign of fear' is the definition.
(I've seen this in another clue)
'doctor scowled at' is the wordplay.
'doctor' is an anagram indicator.
'scowled' with letters rearranged gives 'coldswe'.
'coldswe'+'at'='COLD SWEAT'
(Other definitions for cold sweat that I've seen before include "Chilled perspiration" , "State of extreme nervousness" , "Symptom of nervousness or illness" , "Symptom of fear" , "Chilly perspiration brought on by fear" .)