About to fill in puzzle, jumbo, say (3,7)
I believe the answer is:
for example
'say' is the definition.
(I've seen this before)
'about to fill in puzzle jumbo' is the wordplay.
'about' means one lot of letters goes inside another.
'to' becomes 'for'.
'fill' means to look at the middle letters (I've seen 'filling' mean this (the letters which fill the word)).
'in puzzle' becomes 'frex' (I can't justify this - if you can you should give a lot more credence to this answer).
'jumbo' becomes 'ample'.
The central letter of 'for' is 'o'.
'o' going into 'frex' is 'forex'.
'forex'+'ample'='FOR EXAMPLE'
Can you help me to learn more?
(Other definitions for for example that I've seen before include "By way of illustration" , "Speed" , "Say" .)