Sounds like "glue ear" secondary to a middle ear infection.
How long has this been going on? No Pediatrician visit?
Could it be wax? Some kids do get a hefty wax build up and they make drops to help remove it. I'd ask your pediatrician about that.
Or has the child been fussy or sick? An ear infection can cause a discharge as well. My kids have had all different symptoms when they've had ear infections. The hardest time to tell is when they are cutting teeth. Both my kids got ear infections when cutting various teeth but didn't have normal symptoms of an ear infection. No fever for example.
good luck