Huge firm with a large holding in forfeiture (8)
I believe the answer is:
colossal
'huge' is the definition.
(I know that huge can be written as colossal)
'firm with a large holding in forfeiture' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'with' is a charade indicator (letters next to each other).
'large' becomes 'L' (eg in clothes sizes).
'holding in' is an insertion indicator.
'forfeiture' becomes 'loss' (I've seen this before).
'co'+'a'+'l'='coal'
'coal' enclosing 'loss' is 'COLOSSAL'.
(Other definitions for colossal that I've seen before include "Mammoth" , "Huge, immense" , "Jumbo" , "Giant" , "Extremely large" .)