Help whistleblower restraining falsehood (6)
I believe the answer is:
relief
'help' is the definition.
(I know that relief is a type of help)
'whistleblower restraining falsehood' is the wordplay.
'whistleblower' becomes 'ref' (referee).
'restraining' means one lot of letters goes inside another.
'falsehood' becomes 'lie' (lie is a kind of falsehood).
'ref' going around 'lie' is 'RELIEF'.
(Other definitions for relief that I've seen before include "Easement or assistance to people in need" , "Alleviation of pain or distress" , "Carving style; financial assistance to the needy" , "Relatives" , "Relaxation following distress" .)