Corrosive stuff from ace detectives (4)
I believe the answer is:
acid
'corrosive stuff' is the definition.
(I've seen this in another clue)
'ace detectives' is the wordplay.
'ace' becomes 'a' (abbreviation).
'detectives' becomes 'CID' (abbreviation for Criminal Investigation Department).
'a'+'cid'='ACID'
'from' is the link.
(Other definitions for acid that I've seen before include "Morose" , "Bitter or sour" , "Sour - type of rain or drop" , "Opposite of alkali; sour" , "Caustic and biting" .)