Monks regularly defrost soup in advance (8)
I believe the answer is:
brothers
'monks' is the definition.
'regularly defrost soup in advance' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'soup' becomes 'broth' (broth is a kind of soup).
'in advance' says to put letters next to each other.
The alternate letters of 'defrost' are 'ers'.
'ers' put after 'broth' is 'BROTHERS'.
(Other definitions for brothers that I've seen before include "For example, Marx family members" , "Male relatives" , "Jack and Algy turn out to be (Wilde)" , "See 15" , "Siblings (in arms or in law?)" .)