、。
While I'm out, if anyone calls, tell them I'll be back by five.
Literal
I [of-の] absence during [in-に] someone [from-から] phone [subject-が] exist-[if-たら], 5 o'clock [by-までには] return [quotative-と] tell-put-give.
Three-layer structure: conditional (~たら), an embedded reported statement (~と伝える), and a command. 電話がある is the fixed expression 'there is a phone call / someone calls.' ~ておいてくれ combines ~ておく (preparatory) + くれる (do for me) + command — 'do it for me, in advance.' The command form くれ is masculine/casual.