Unreasonable custom husband omitted a lot (1,3,4)
I believe the answer is:
a bit much
'unreasonable' is the definition.
(thesaurus)
'custom husband omitted a lot' is the wordplay.
'custom' becomes 'habit' (habit is a kind of custom).
'husband' becomes 'h'.
'omitted' is a deletion indicator.
'a lot' becomes 'much' ('much' can be a synonym of 'a lot'**).
'habit' with 'h' removed is 'abit'.
'abit'+'much'='A BIT MUCH'
(Other definitions for a bit much that I've seen before include "over the top" , "Taking liberties" , "unfair" , "Somewhat excessive, crossing the permitted line" , "That's not on" .)