Of or pertaining to the characteristics of a work of art in which forms and rhythms are defined chiefly in terms of line (6) - I make this to be linear -I-E--
It links to 18 down which is
The works of a writer, painter or the like, taken as a whole (6) O-U--S
I think this is opuses but the two dont link together. The last letter in 23 across is the 5th letter in 18 down
By the way - this is a really clear set of clues now, but you could have added this to your previous post, rather than starting a new one.
I hope this helps!
I should say I'm typing for my father here - so you could get another question next sunday with half the information until he gets the hang of this himself!