It should be OK. Fairy wrasses are model reef citizens. Although I've only ever had one tank that housed both clams and a fairy wrasse at the same time, most of the fairies that I've kept were in tanks without clams. But I did have a
Cillhilabrus lubbocki in with clams and he never ever bothered the clams.
Here's a good article about fairy wrasses:
http://www.reefkeeping.com/issues/20...hcs3/index.php