Informer provides material for insider trading (5)
I believe the answer is:
I believe this is a double definition.
'informer' is the first definition.
(snout can mean a police informant)
'material for insider trading' is the second definition.
(cigarettes or 'snouts' are traded inside prisons)
'provides' acts as a link.
(Other definitions for snout that I've seen before include "nose of pig" , "Tobacco -- hooter" , "Pig's nose" , "Schnozzle" , "Nose; tobacco (slang)" .)