We sold cat spraying fluid produced when frightened (4,5)
I believe the answer is:
cold sweat
'fluid produced when frightened' is the definition.
(you might sweat when scared)
'we sold cat spraying' is the wordplay.
'spraying' is an anagram indicator.
'we'+'sold'+'cat'='wesoldcat'
'wesoldcat' is an anagram of 'COLD SWEAT'.
(Other definitions for cold sweat that I've seen before include "Chilled perspiration" , "nervous reaction" , "Symptom of nervousness or illness" , "State of extreme nervousness" , "Symptom of fear" .)