Area of commerce functions aboard double-decker? (3,8)
I believe the answer is:
big business
'area of commerce' is the definition.
'big business' can be an answer for 'commerce' (thesaurus). I'm not certain of the 'area of' bit.
'functions aboard double-decker?' is the wordplay.
I cannot quite see how this works, but
'functions' could be 'sines' (sine is a kind of function) and 'sines' is present in the answer.
'double-decker?' could be 'bus' (synonyms) and 'bus' is located in the answer.
The remaining letters 'big' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for big business that I've seen before include "Large commercial enterprises, collectively" , "Large-scale financial activity" , "Powerful firms" .)