Risk about a grand (8)
I believe the answer is:
'grand' is the definition.
'risk about a' is the wordplay.
'risk' becomes 'imperil' (I've seen this in another clue).
'about' is an insertion indicator.
'imperil' enclosing 'a' is 'IMPERIAL'.
(Other definitions for imperial that I've seen before include "Of an empire or its ruler" , "Supreme, august; a beard" , "Regal - type of beard" , "Like some rulers" , "Mint --, sweet" .)