に当たって[niatatte] at the time of (ind. opportunity or situation where something should be done)
一騎当千[ikkitousen] being a match for a thousand
一指当たり[ichiyubiatari] span
一人当たり[hitoriatari] per person
一人当て[hitoriate] per person

引当[hikiate] mortgage
引当金[hikiatekin] reserves
押し当てる[oshiateru] to push (something) against
穏当[ontou] proper
過当[katou] excessive

一眼[ichigan] one eye
一眼レフ[ichiganrefu] single-lens reflex camera
一隻眼[issekigan] sharp eye
遠眼[engan] farsightedness
遠眼鏡[toomegane] spectacles for far-sightedness

凹眼[ougan] cavernous eyes
凹眼鏡[ougankyou] concave glasses
開眼[kaigan] enlightenment
眼下[ganka] under one's eyes
眼科[ganka] ophthalmology