Sorry for my bad english.
In CCleaner in the section "cleaner" there are two lists:
"Windows" and "applications".
How can I remove a software entry from the applications-list?
I am a user of MS Office 365 and in the applications-list there is an entry "Office 2013" an an entry "Office 2016". How can I get rid of the first entry?
if you sure that you don't need "Office 2013" cleaning, then you need to delete this key
HKCU\Software\Microsoft\Office\15.0\Common
if you don't know how to handle registry editing, just leave the entry un-tick
WHOA - HOLD UP THERE.
Removing that reg key will effect the whole PC, not just CC.
The key isn't there for CC's benefit, it's there for Office usage.
I'm guessing you had Office 365 (2013 version) and due to the subscription, have now automatically upgraded to 365 (2016 version).
You need to double-check, now you have the 2016 version, that the 2013 stuff (known as v15.0) isn't still required or referenced somehow.
Perhaps use the /EXPORT switch to find where/why CC is detecting your Office 2013 from.