Make hush money (4)
I believe the answer is:
dosh
'money' is the definition.
(I've seen this before)
'make hush' is the wordplay.
'make' becomes 'do' (doing is a kind of making).
'hush' becomes 'sh'.
'do'+'sh'='DOSH'
(Other definitions for dosh that I've seen before include "Money (sl.)" , "currency" , "Ready" , "Spondulicks" , "Shod (anag.)" .)