Depression of standard in credit (6)
I believe the answer is:
crater
'depression' is the definition.
(I know that crater is a type of depression)
'standard in credit' is the wordplay.
'standard' becomes 'rate' (I've seen this in other clues).
'in' indicates putting letters inside.
'credit' becomes 'cr' (abbreviation).
'rate' going into 'cr' is 'CRATER'.
'of' acts as a link.
(Other definitions for crater that I've seen before include "Large bowl-shaped hollow" , "Bowl-shaped cavity as on volcano peak" , "Geological depression" , "Great hole as on top of volcano" , "Bowl-shaped opening" .)