Crossword Genius

Bad forefathers I worked out to be group of similar type (5,2,1,7)

Ross

I believe the answer is:

birds of a feather

I'm a little stuck... Click here to teach me more about this clue!

'be group of similar type' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'bad forefathers i worked out' is the wordplay.
'worked out' indicates anagramming the letters.
'bad'+'forefathers'+'i'='badforefathersi'
'badforefathersi' with letters rearranged gives 'BIRDS OF A FEATHER'.

'to' is the link.

Can you help me to learn more?

(Other definitions for birds of a feather that I've seen before include "they combine well!" , "like-minded people" , "Likes" , "sitcom" , "Like people" .)

I've seen this clue in The Telegraph.
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