Husband's mistake at home? Gutting ginormous fish! (8)
I believe the answer is:
herrings
'fish' is the definition.
(I've seen this before)
'husband's mistake at home? gutting ginormous' is the wordplay.
'husband' becomes 'h'.
'mistake' becomes 'err' ('err' can be a synonym of 'mistake'**).
'at home?' becomes 'in' ('in' can be similar in meaning to 'at home').
'gutting' suggests removing the centre (I've seen 'gut' mean this (gut can mean to remove the insides of)).
'ginormous' with its middle taken out is 'gs'.
'h'+'err'+'in'+'gs'='HERRINGS'
(Other definitions for herrings that I've seen before include "Silvery fish of shallow waters" , "may be in fishnet" , "Tasty North Atlantic fish, sometimes red" .)