Rings after husband leaves? Oh dear! (4)
I believe the answer is:
oops
'oh dear' is the definition.
(both are said in recognition of a mistake)
'rings after husband leaves?' is the wordplay.
'rings' becomes 'oo' (multiple circles).
'after husband leaves?' becomes 'ps' (I can't explain this - if you can you should believe this answer much more).
'oo'+'ps'='OOPS'
(Other definitions for oops that I've seen before include "My bad" , "Exclamation of making a blunder" , "Oh dear, I've spilt something!" , "Silly me, I've dropped something!" , "Exclamation on making a minor mistake" .)