Blunder by big broker wielding clout to talk irrelevantly (2,3,2,1,7)
I believe the answer is:
go off at a tangent
'broker wielding clout to talk irrelevantly' is the definition.
I know nothing about this answer so I can't tell whether this works.
'blunder by big' is the wordplay.
I cannot really understand how this works, but
'blunder' could be 'goof' (synonyms) and 'goof' is located in the answer.
'by' could be 'at' and 'at' is found in the answer.
'big' could be 'fat' and 'fat' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for go off at a tangent that I've seen before include "Suddenly change course" , "Diverge" .)