The most common and most likely answer to this crossword clue is the 4 plus 6 letter word LOVE AFFAIR
I've seen this crossword clue in The Sunday Telegraph
L
O
V
E
A
F
F
A
I
R
More clues leading to the result LOVE AFFAIR
- What gets one amazingly alive for embracing a female?
- Great enthusiasm for redeveloping very old flea market
- Romance is nothing connected with business
- Nothing fine about a fine romance!
- Romance with a female, beautiful with nothing on
- Like a loud blonde’s relationship?
- 15 next business 16 3-7
- Avail offer to break up the romance
- Intellect welcoming valentine’s lips, just romance
Buddy explains!

The straight part
We know that "omance!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case omance! = love affair.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.