Now happening to bring work forward? Such an illusion! (7)
I believe the answer is:
optical
'such an illusion' is the definition.
(I've seen this before)
'now happening to bring work forward?' is the wordplay.
I cannot quite see how this works, but
'work' could be 'op' (common abbreviation for 'opus') and 'op' is found within the answer.
The remaining letters 'tical' 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 optical that I've seen before include "Topical (anag.)" , "Capitol (anag.)" , "Relating to sight" , "Involving light" , "some kind of illusion" .)