Yes, tuck is a Scrabble word!

Verb

1. Fit snugly into

2. Make a tuck or several folds in

3. Draw together into folds or puckers

Noun

1. Eatables (especially sweets)

2. (sports) a bodily position adopted in some sports (such as diving or skiing) in which the knees are bent and the thighs are drawn close to the chest

3. A narrow flattened pleat or fold that is stitched in place

4. A straight sword with a narrow blade and two edges