The term 'EYE PART CONTAINING THE IRIS' can be solved by the four-letter word 'UVEA'. The uvea is a part of the eye that contains the iris, which is the colored part of the eye. It is also known as the uveal tract and is composed of three layers: the choroid, the ciliary body, and the iris. The uvea helps to regulate the amount of light entering the eye and also helps to protect the eye from damage.