The most common and most likely answer to this crossword clue is the 4 letter word GRIN
I've seen this crossword clue in Independent
G
R
I
N
More clues leading to the result GRIN
- Look happy when dull work is nearly done
- See female leaving opera gives smile
- Smile broadly, having right to dip into drink
- Feeling vexed when cha’s off? Don’t look so miserable
- Expression of pleasure as tedium’s cut short
- It’s an endless chore to smile
- Show amusement as Romeo is caught in a trap
- Smile broadly and run into trap
- Laugh at the end of Wagner opera
- Smirk as Romeo is caught in trap
Buddy explains!

The straight part
We know that "show ivories happily with it" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case show ivories happily with it = grin.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.
What does GRIN mean?
GRIN noun- A smile in which the lips are parted to reveal the teeth.
- To smile, parting the lips so as to show the teeth.
- To express by grinning.
- To show the teeth, like a snarling dog.
- To grin as part of producing a particular facial expression, such as a smile or sneer.
- A snare; a gin.