Crevice, Crack, Gap, Opening
noun
A crevice interval is an area with a crevice or crack.
すきま
The reading for 隙 is the one you learned with the kanji and the 間 is the 間に合う reading.
二台の自販機の隙間に、小銭が2-3枚落ちているのを見つけました。
I found a few coins in the gap between two vending machines.