Corroborate name in accordance with detective to begin with (8)
I believe the answer is:
underpin
'corroborate' is the definition.
(I know that corroborate can be written as underpin)
'name in accordance with detective to begin with' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'in accordance with' becomes 'under' (I can't explain this - if you can you should give a lot more credence to this answer).
'detective' becomes 'PI' (private eye).
'to begin with' means one lot of letters go next to another.
'under'+'pi'='underpi'
'n' put after 'underpi' is 'UNDERPIN'.
Can you help me to learn more?
(Other definitions for underpin that I've seen before include "Prop up with nun pride" , "Form the basis for" , "Support or strengthen from beneath" , "buttress" , "corroborate" .)