Keep talking of how there's a great demand for? (3,2)
I believe the answer is:
run on
'keep talking' is the definition.
(I've seen this before)
'of how there's a great demand for?' is the wordplay.
I cannot really understand how this works, but
'of' could be 'o' and 'o' is located in the answer.
'there's' could be 'n' (I've seen this in other clues) and 'n' is present in the answer.
The remaining letters 'run' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for run on that I've seen before include "Talk continuously" , "continue without interruption" , "Go past the normal finishing time" , "Keep talking" .)