Help beat mixture (4)
I believe the answer is:
abet
'help' is the definition.
(I've seen this before)
'beat mixture' is the wordplay.
'mixture' is an anagram indicator.
'beat' anagrammed gives 'ABET'.
(Other definitions for abet that I've seen before include "Beat up by way of help" , "Assist criminally" , "Assist (in doing wrong?)" , "Urge on, help" , "Egg on" .)