Steep charge to support staff (8)
I believe the answer is:
macerate
'steep' is the definition.
(both can mean to soak in a liquid)
'charge to support staff' is the wordplay.
'charge' becomes 'rate' (rate is a kind of charge).
'to support' says to put letters next to each other (in a down clue, some letters hold up others).
'staff' becomes 'mace' (a mace is a ceremonial staff or stick).
'rate' put after 'mace' is 'MACERATE'.
(Other definitions for macerate that I've seen before include "Soak" , "Soften food by soaking" , "Cream tea (anag) -- soften by steeping in liquid" , "Steep in liquid like cream tea" .)