Sindarin translation

How to translate "captive/unfree sunlight" into Sindarin? It would be interesting to get a proper name and a separate common noun

Mae govannen Irien!

Well there is no Sindarin word for captive. We do have:

• S., N., ᴱN., G. band [mb-] n. “prison, custody”
• ᴺS. !banna- [mb-] v. “to imprison”
• ᴺS. !bannan [mb-] n. “prisoner, (lit.) imprisoned-one” ᴺS. [S.] ast n. “light or heat of the sun, *warmth”

captive/unfree is an adj. describing sunlight. So it would yield ast mbannen meaning "imprisoned light of the sun"

A name possibly proper name could be bannast but this could be confused with the intransitive verb banna-

As always wait to hear from others.

Thank you! And how could the name sound?

You're welcome. So I can give the IPA: 'bɑn.nɑst that would be the closest to how it sounds. And you can check out here Eldamo is a great source.