Otherwise Mrs Alf Garnett (4)
I believe the answer is:
else
'otherwise' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for else that I've seen before include "In addition; different" , "Eels (anag)" , "Besides; instead" , "As an alternative" , "Otherwise; different from" .)